Introduction to Logic

r reasoning
going from what's known to what's
unknown
and so he taught him these things and
then he said
i want you to go into the marketplace
spend the day in the marketplace and
come back
so he went spent the day in the market
he finished his because he's going to
give me jazza and mantel
right so he went to the marketplace
spent the day in the marketplace he came
back
he said how was your day
he said i did what you told me i was in
the marketplace all day he said
did you notice anything he said no
he said you're not ready we need to do
this again so
they studied logic second course
did it all understanding judgment
reasoning finished his course
so he said to him i want you to go and
spend the day in the marketplace
okay so he goes spends the day in the
marketplace
comes back he said how's your day in the
marketplace all day just like you told
me
nothing he said we have to do this again
did the course in logic again went
through the three operations of the mine
when he finished it he said listen i
want you to go to the marketplace spend
the day in the marketplace
come back he goes spends the day in the
marketplace comes back
he said how was your day
he said oh my god i couldn't believe it
they're all practicing logic
he said now you're ready he gave missy
jazza
because that's what that's what it is
the whole world is
people reasoning making
understanding basic things
asserting things or negating things and
then making arguments
that's what's going on everywhere you
look that's what's going on
come in there's a discount today
all right there's a discount today
so what's going on in the mind oh
if i buy today i'm going to save money
therefore i should buy today
right it's logic the whole thing is
predicated
on reasoning and that's what the student
finally got that it's happening all
around you
and that's one of the really interesting
things about studying logic
is that you begin to
refine that process and are better able
to understand what's being said to you
and better able to communicate what you
want to say to others
so i just want to show you
this is the book by sidi ahmed zarrow
called
and i'm going to read two kawaii and
talk about them quickly and then we're
done
the first kaidah he says fisher
[Music]
[Music]
of him so he says
that kalam before we can talk about a
thing
in other words before we can do make
judgments about things
we have to understand what the nature of
that thing is
this is a qaeda before you can make a
judgment about a thing you have to
grasp what that thing is so this is what
he's saying he's saying
that at kadam
it is a branch of comprehending its
essence
and and comprehending what its benefit
is
be sure so this occurs in the mind
mukhtasebin al-badihiyan it either
occurs discursively
through reflection through being taught
or it's intuitive you just grasp it
immediately so you have immediate
knowledge
and then you have mediated knowledge so
immediate knowledge is two is greater
than one
nobody needs to teach you that a child
will understand that
but that one that 2.5 percent
in zakat is 140th that's
that you have to understand because you
need to understand what
fractions are you need to understand
what decimals are and you need to
understand the relationship between the
two
so that's a different type so those are
the two types so he's saying
that before we can speak about something
we have to grasp
what its essence is and what its benefit
is through this
mentation through this mental
rashi assignation would be a big word
for it in the west
and then he says in order
these are all logical concepts so this
is called extension
in logic so the afra that this is
all those things that it extends to
because you have what's called
comprehension
and extension all right the
comprehension
is is the the or the understanding of it
what it is and then uh
what it applies to all the things that
it applies to
so in order for you to for it to be
understood through it
and also the encouragement to know it's
to know its benefit we'll encourage you
to study it
and to to be able to articulate
its subject matter and so you should
understand this so here's the beginning
of a book on
which is all based on mantak
like you cannot understand this if you
haven't studied manta
so here's a this is our tradition if you
read tafsir
if you read apida if you read
any of the major sciences of islam
especially
you will find that they're all relying
on the the reader's understanding of
this mustard
and not just these but several other
sciences especially when you get into
the later scholastic tradition
by the time you get to somebody like
he's he's got bellare going he's got
mantak going he's got grammar going he's
got what that going
it's it's a mustar hadith
all of these subjects he was well versed
in
and this is how he's teaching
so then he says
the essence of something is its reality
the the essence of a thing
is its reality to understand the essence
is to understand the reality
right
and its reality is what
it it's some summarily means what it
means by summation
what it can be summed up into
with and the definition of that
is through ahad which is a term
in latin terminus means the end of
something so a term
is is the end of something in arabic had
is the end of something
so the head is the end of something and
so this is
that's that is the most comprehensive is
as a definition but then you have what's
called a rasam
which in western logic is called the
descriptions so something
and and when we get into i'm just giving
you this is just
a you know it's like at the restaurant
when they give you a sample
so don't we're going to go into this in
detail over the course
of the next couple of weeks inshallah so
don't worry about not getting any of
this
right now when when you get a hadoo or
something you need to know what are
called the five predict predictables
which are the al-father khamsa
right so you have gins the genus you
have the knot the species
you have the hassa the differentia and
then you have
the the the the the um the arab
which is like the it's uh you have the
proprium
which is the uh and then you have the
fossil sorry the fossil which is the
differentiate the hasa which is the
propium or the property
and then you have the arab and some call
the those two types of
accidents the aradon lazy moon and then
so those five things are going to enable
you to give the hud
the definition or the description the
hud is is
is the genus and the difference
so the genus is what you can say about a
lot of things
the khasa is what's specific to that one
thing
so with a human being what's our
definition traditionally in
in in logic
what do they call the human being
what's that
which in arabic means the speaking
animal but they really mean the rational
animal
in the west we call it the rational
animal so our genus is rational
this is different from biology because
you know they talk about genus and
species so yeah those are biological
terms this is logical terms they're two
different sciences
so don't get them confused the gene i
mean they're they're related but they're
used
very specifically in in these sciences
for different for
things that they mean in that science so
the the
the genus is the general
and then the the the the fossil
is the difference so with the human
being we're an
animal but many types of animals so what
makes us unique what's the fossil
what differentiates us from other
animals rationality
this is the definition so this is a
logical definition
everything can be defined in this way
and this is the foundation of defining
things
because when we speak in language when
we want to know what
is right what is us
very often it's in the thing itself
if you understand those two words then
you'll understand what the definition
of us is and these are called
right so this is this is how this works
and so he says
the the rasam the description is clearer
or it can explain something
it helps you understand it quickly
see now all of this was to introduce the
definition of tasawolf
all of this so he's given you now he's
told you before we can talk about
something we have to define it
what's its definition it's it's reality
what is the reality of tasawolf
has been defined it's been described and
it's been explained
in many many different ways
it will reach up to about 2 000
different definitions
all of those definitions go back
to one fundamental meaning
sincerity in your
god-directedness
its sincerity in your inner direction
towards your lord
that's the definition
so what does that mean what it means is
the genus of tasawolf is ichlas
that's the genus it's sincerity
but the difference because you can be
sincere
as a doctor you're sincere like you say
he's a very sincere
doctor just means he doesn't cheat you
he's doing what should be done
right so that's the genus sincerity
applies to many many different things
he's a sincere student
he's a sincere son
we can apply that but what is the
difference
what's the fossil it's sincerity
in your directedness towards god in
those things that apply
to your lord so you are sincere in your
ibadah
you are sincere in your muammar for the
sake of allah subhanahu wa tala that's
tasawolf and that's why you can be a
sufi
and and and be
like have nothing to do with that word
there's people
in in in uh
places that they might even not even
like tessault
they don't want to have anything to do
with it but they have sitka
to allah and in that way they have tasov
so the name is just a name
what's the reality of the name if you're
stuck on the name you're a nominalist
the name is just a name whether you call
it tasw
right whatever you call it it doesn't
matter those are names
the muslims for centuries called it
tasawolf there's no reason to abandon
that name really there's no reason
there's people that have tried to get
rid of it
but there's no reason to abandon it once
you clarify what it is
and the early the earliest sufis imam
al-junaid said
no one can speak about this matter that
hasn't mastered the book and the sunnah
that's what imam junaid said
imam tasturi said i hear
things about this matter but i always go
to two just
witnesses to hear their testimony
the book and the sunnah and this is why
siri ahmed zarooq says
the sufi has to submit to the faki
and the fakie doesn't have to submit to
the sufi
if your tasof is not in accord and not
some narrow-minded provincial faki who
only has one way of doing thing no
to the broad-based interpretive
tradition of the fukaha which includes
the methodology
of the great imams of this ummah so
there's imams that say
that you can do the maulid and that's
the majority of the later scholastic
reason there's
imams that say no don't do that that's
fine it's a hilar issue
if you don't want to do it that's fine
but if you do do it
it has to be free of things that are
moon karat
but to say it in and of itself is a
munkar
no because
the worst that can be said about it is
that it's macro
according to the uluma but to say that
it's prohibited or something like that
i mean that's an extreme position that
very few scholars ever took so anyway
that
that's my introduction so inshallah
tomorrow i'm going to
start with the 10 mabadi which
are foundational in our tradition what
are called the body
one of the great 18th century scholars
versified the 10 my bad in that it's in
your book
and then i versified it for you in
english if you want to memorize it in
english
so those are the ten mibadi i'm going to
do those tomorrow inshallah and that's
usually that was the introduction
to any islamic science always began with
this it begins from an early period
they started doing this and the reason
for it was to give the student
a comprehensive view of the subject
before you went into it
it's like seeing the forest before the
trees
which helps just to see the whole thing
before you go in and say okay that's an
oak and that's the elm tree and that's
an acacia tree and
just to understand what a forest is and
so
the subject is uh
is uh part of that and the name
and its sources where it comes from
it's also it's ranking one of the things
that we fail to do now
in in western education we don't rank
knowledge anymore so
nobody knows what's more important i
mean if you go
if you look at the if you go to any
college
most of you have been to college some of
you are in college some of you are going
to be going to college
next year or something if you go to
college they have these
catalogs they begin with astronomy and
they end with zoology
this is a to z
there's no ranking they don't tell you
what you should take
what's important this is more important
than the other muslims
always rank their sciences it's called
the
or
what's the virtue of the science and the
shut-off is
what it what the subject matter so if
the subject matter is god
it's a very high science if the subject
matters dunya
it's the lower science if the subject
matter is language it's a very high
science because it's a
it's a tool to understand god
so these are the rankings hierarchical
nature of science because we believe in
marathi there are degrees of knowledge
there are degrees of existence we have
four levels of existence you know
there's degrees in our tradition of
existence then you have
metaphysically you have other realms as
well the molk the markov
so um anyway
questions answers
dumbfoundedness
any questions
i've been teaching for about 10 years
and
obviously before that i was a student
and i'm worried that modern education
has
deconstructed our reasoning skills and
we'll
if if it has in your opinion do you
think we'll need 13 years to reconstruct
them also
yeah i mean you know the modern world is
it's in a mess i think all of us are
pretty aware of that
and that's not to say that the
pre-modern world wasn't either
in some ways there's a lot of good and
and in in some ways this is one of the
better times that people have been
living
so um i'm not completely dismissive
of uh the modern world but there are
there are
things about the educational system in
the past that were very problematic
and but there are things with the modern
system of education that are also very
problematic
um there are still places where you can
get a reasonably good education
i would say but in terms of
those basic fundamental skills that are
very important to grasp
and should really be learned at a
relatively early age
in the west they they were grammar and
logic and rhetoric and then also the
skills of numbers so these are the two
types of literacy what we call uh
literacy with language and then numeracy
or literacy with numbers
and these are the two ways that human
beings think
we think qualitatively which is
linguistically through language and then
we think
think quantitatively through number so
and when we get into the categories
which are part of the tradition of logic
there are ten categories
and after substance you know the two
categories
that immediately follow that are
quantity and quality
come and cave in arabic and so
we it was a book by a french philosopher
the turn of the century it was written
the reign of quantity and a lot of
people noticed this about the modern
world that it was a world of quantity
and quality was being taken out of the
world
not completely and not entirely but
quality is
much less important to the people today
than it ever has been the idea of
mastery
is is is we have mastery in a few things
i think in music there's still a
commitment to mastery
uh in certain sports there's a
commitment to high levels of mastery
but the idea of mastering the mind the
idea of mastering the soul
the idea of mastering arts and crafts
becoming
great craftsmen becoming uh really
you know masters of these things it's
very very unusual
in the modern world to meet people that
are really committed to mastery of
anything
and obviously the highest thing is to
master yourself
and that is very difficult
ahmed zarook said it's easier to move a
mountain with your fingernails than it
is to actually transform your
nature so it's but it is possible and
imam razadi
argued that anybody who claims that you
cannot change
nature is a liar and he said
you can you can take a dog and train a
dog
and he's saying what you can't
you can't take a human being that has
rational
nature and not transform it
you know you can take a dog that has you
know
all over the place and teach it to do
very relatively sophisticated tricks
and teach it to sit and what you can't
discipline the self
you can a dog you can discipline but
your own self
you can't teach it to stop don't do that
it's not good for you
you know this is incontinence which
is a beautiful word in in in the
19th century in america and it was a
moral term it wasn't a medical term
and and and continence is
is the idea of restraint self-restraint
incontinence
is ecracia or the lack of self-restraint
now it's been reduced to
incontinent to stool and urine this is
this is what's been reduced to people
that can't control their most basic
bodily functions
are called incontinent but in reality
you should be able to control your your
nature
and and this takes time it takes
practice and it takes skill
but the modern world wants to strip that
away so
certainly learning these skills are very
important
uh in in the in the modern world
logic has been reduced to what's called
material logic and we'll get into that
in the third
lecture uh we'll get into
material logic you have formal logic and
material logic material logic
one aspect of material logic is called
the fallacies which are called the
safsatta
or the mohawk are
fallacies of reasoning so it's the
content of your logic
and and we we uh
we're very susceptible to them
politicians are
use them all the time and we're very
susceptible because the mind is
susceptible to hasty generalizations
i mean i'll give an example if you look
on if you watched cnn
before coming to turkey you probably
would have cancelled your trip
because they made it appear that this
whole country was in revolution
and when when you got here in istanbul
you're there and it's it's very peaceful
and it's so ludicrous for people in new
york don't go to turkey you know it's a
dangerous place you know they're all
they're gone crazy
you know meanwhile there's people
getting mugged all over the place in
central park right i mean this
this is so much safer than being
in new york and but you know people are
afraid to come to turkey because they
watch the news
and the news is constantly using
fallacies
and sometimes it's just pure deceit
but you know i mean they said for
instance how many people heard that they
were going to tear down all the trees to
build a mall
how many people heard that okay that
look at that
that was a complete lie they weren't
going to tear down
they were actually going to remove some
trees around the edge of the park
to to restore the fort that had been
torn down
it was an ottoman military base and they
were going to make a museum
they weren't building a mall right so it
was this kind of oh this massive
you know this insane liberal capitalism
gone mad
turkeys on steroids they're going to
turn everything into malls
no they were going to preserve the trees
make a museum
and the so-called mall was actually
cafes
around the area for people to
enjoy the the place but
it's a very very uh
secular part of istanbul
and some of the people there the
majority of pubs in istanbul are in that
area
and because they put a 10 p.m
limit on sale of alcohol which is the
case in many states in america
right they have these laws i mean you
have many many cities in the united
states where you can't sell alcohol
after and then you have dry days it
wasn't that long ago before we had dry
states right so
this whole idea that you know oh that no
you can't do that
if if they see fit to uh if they
if if they're having problems with uh
with
um disorderly contact because of the
sale of alcohol
then that's part of what public order is
you have to succumb to the public order
but if you looked at it you know these
these were
these are tactics people can't think
clearly anymore
they showed a picture of a million and a
half people
and cnn said oh this was a protest
against the president no it was actually
a protest for the president
a demonstration for the president and
then cnn retracted that a little later
and said oh whoops we made a mistake
that was actually a pro
presidential you know so the people
opposed to it were a few hundred people
that they gave nine hours of
unprecedented
live coverage on cnn international i
mean where were they when iceland was in
rebellion against
the the uh the parliament because the
banks
they weren't going to pay the banks
where were they how many people got to
see all the greek
rebellions and the abuse that the greek
protesters took from
i mean you know you
need the tools of thinking in the modern
world because
you're up against a massive propaganda
machine and it's it's a propaganda
machine that
is is not so much a conspiracy but it's
just
they all think the same way they look at
things the same way
and so turkey because turkey is
a a a a country that has
a very very troubling um history for the
west
turkey was once the center of one of the
most powerful
dynasties in human history and had an
empire
that was unprecedented and lasted for
a very long time and there are people
that
there there's a little bit of
schizophrenia in the country they were
deeply traumatized
i mean imagine imagine in
in united states or in canada imagine
obama announces we have decided
that starting tomorrow all of english
will be written
in the pinyin chinese script because we
realize that china
is a rising power and we want to prepare
our young people
early so that they'll be able to read
chinese
so tomorrow all the textbooks are going
to be published in chinese script
it's still english don't worry you're
not going to be saying nihoma you'll
still say how are you
but it's going to be written like the
chinese write their script
i mean imagine the trauma that that
would cause in a nation
and that's what was done here they went
from their arabic ottoman script
to a latin-based script overnight
and then imagine the trauma to the kurds
of prohibiting them from speaking their
language this is what happened to the
native americans
they were prohibited to speak their
native languages in the united st
to speak their native languages on the
reservations
right imagine that and here
for the first time now they've
they're they're allowing them to teach
their language to teach
this is what they've done so this
so-called fascist turkish government
that's being presented to western people
is is removing a lot of the the
the darkness that had descended upon the
people from before
but people are very worried you know
there's people that are secular and they
think oh these are the muslims taking
over
well they're muslim people but they're
committed to a secular state
right and and and the idea that islam
and secularity are mutually exclusive is
false because the vast majority of
islamic history
had relatively secular states they
they weren't really islamic states the
whole
concept of an islamic state is a fantasy
in in the in the minds of a lot of the
modern islamists
but if you actually study
muslim history that you will find yes
islam was the state religion
but the states functioned
just like a secular state functions
because religion actually has very
little to do
with the running of a state
building roads has nothing to do with
what meth have you follow
you know oh that's a hanafi road no
that's a medhab
right the madhhab is means road in
arabic but medhep is a school
is a metaphor taken from the real method
which is a road no a road is you can
build it from
stone you can build it from asphalt you
can build it from concrete
and that's just what you want is honesty
you want vetting you want transparency
those
are secular ideals as well right
a post office is not an islamic concept
right the you don't need we need islamic
stamps
yeah you can have put okay put the head
of like muslims
on their coins okay in america they have
kind of laid
allah that's
right all right that's okay america's a
secular state it still has to
not allah right so that's okay you can
have
god we trust it's not you can be secular
and still
trusting god it's okay right
municipalities are not you know the the
water doesn't
i need a hanafi you know they call it
hanafiya in arabic
i need a hanafi hanafiya this is a
maliki hanafiya
no you don't need you just need a
hanafia you just need a
a water right tap that works
and that's municipalities and all you
want is some honest guy in there if he's
a secularist who's honest
fine if he's a muslim who's honest fine
as long as the water gets there
it's been purified it's not going to
make you sick right
seriously think about it the vast
majority of government just does not
relate to religion it just relates to
common decency
and that's why you can live in i mean if
muslims
were were literally taken from like 8th
century
uh syria or palestine and dropped into
norway
they would think that you know it was
like the caliphate of omar ibn abdul
aziz
like there's so much social justice they
would be amazed
at how much social justice are in these
scandinavian countries
they're secular countries so this whole
idea
no you have to have had punishment
you know this this is what so islam is
reduced to there's
four agreed upon had punishments 13
there's debates about you know sir even
apostasy laws all these things they're
all debated
there's nothing fixed in stone and then
the the prophet saw i sent him he said
avoid implementing penal punishments as
much as you're able to
maybe no we want to cut and let's get
these hands cut off
you know i mean if you had if you
implemented had punishment for theft
you you couldn't shake hands anymore
you wouldn't be able to shake hands
everybody'd be like you know
nice to meet you right from from the
from the president all the way down to
the street sweeper man we would am i
making this up
[Music]
so you know anyway that's a very long
answer to a very short question
so oh know
would you recommend a book for beginners
to read on logic well that's what we're
doing it's a beginning book on logic
miriam joseph's book is very good for
and and it helps if if english is your
first language
it definitely helps to study logic in
in english before you do it in arabic my
own personal experience
i read it in arabic it was very
difficult for me initially
and after i studied it in english i
studied it several years ago
using aristotle's text with my father
and and
after that it it when i went back to the
arabic it was just very
much easier to do so and there's there's
good but it's important to note that
this is
traditional logic it's not symbolic
logic which is very different symbolic
logic is a type of uh
mathematical logic
that um it's useful for certain things
um but for reasoning
uh in terms of language
it's not very it's not useful at all
because of
certain problems that it has
associated with it all right so
alhamdulillah
i just want to also for the people that
are online just welcome you
uh for um
being part of this and everybody we i
really hope inshallah you have a
wonderful experience your time
in turkey there they've been incredibly
hospitable it's a beautiful people
they're good people
um and they're all types
of people there's and the whole spectrum
is here in turkey but they're still very
decent people whether they're
secularists or committed to islam
i think you'll by and large find a very
very
a lot of just human decency that's been
my experience
i've been in turkey now several times
and spent
you know periods close to a month
a couple of those times and that's been
my experience with the people
from the top all the way down
to you know the simple people
um and they and it's a great tradition
they have a great tradition here
and and they're also i think one of the
things that i really like about turkey
is
um they still have an aesthetic sense
that a lot of muslim countries have lost
so they
they tend to really beauty is still very
much part
of their culture and they have beautiful
parks they have beautiful
a lot of beautiful architecture still um
istanbul is arguably i think the most
beautiful city
aesthetically outside of
medina because i'm not going to say
anything is more beautiful
than medina i mean now medina is the
mosque
uh alone and it's a very beautiful
mosque
it's the most beautiful mosque in the
world and um
so but after medina i would definitely
say
i mean i was in istanbul and i said to
this
turkish man he told me he'd studied in
san francisco i said oh that's uh that's
our is
that's our istanbul and he's like
i said you know the bay it's got water
and
hills and he just went no
no no it's uh
and also make dua for the organizers
they've worked really hard
dr aisha and her team really sincere
group of people
worked very hard to make all this happen
so inshallah may allah make it a blessed
time for you a time of learning and
opening
and my advice to you is you know don't
turn on the tv
uh try to avoid you know
just unplug
for a little while you know you're all
plugged in
it's good to unplug for a while and
and just try to focus on your studies as
much as possible
we didn't plan having a mall next to us
so my advice don't go into the mall
dr yang is coming tonight so we we
traditionally we always had an exercise
component in the rela and then
joseph uh who used to do
the do you remember joseph he in new
mexico and things he used to do the
tai chi and the kung fu
and he died so after that
we just didn't do it but we'd always had
that component because i
you know i think it's very important for
people muslims tend to neglect their
bodies a lot
and uh traditional societies there was a
lot of exercise just
being in a traditional society walking
and uh
horseback riding and archery and uh
wrestling
all the prophet sam was a very active uh
all the way through his whole life he
was physically very active
he did had no fat on him so allah did
he he was described as having a very
flat stomach
even when he was 63 years of age he was
very muscular he's sinewy and very
strong
and uh omar binarb once saw a man who
was overweight
in mecca and he said that would be
better if it was on somebody else
right so in other words your extra
caloric intake
you know might be better if you give
that to somebody else now don't
judge anybody because some people have
uh you never know about people so if you
see people that are overweight
you know just don't be judgmental about
them or arrogant or anything because
some people they really
they don't eat a lot and in fact imam
banani says that some of the olia
are tried with fat like allah makes them
fat even though they don't eat anything
and and i've seen that with some people
you know that
so you know don't don't make any
judgments about people about that and i
don't want people to feel bad
or anything like that but it's good just
to do exercise
you can be women should you know
traditionally they were
you know had good weight
and and so there's no blemish in a woman
who's got
weight on her it's actually healthier
for a woman to have fat
uh you know really so
this these skinny women end up losing
their
their periods they can't have children
and you know this happens like they do
too much exercise
and they actually um
end up losing their femininity and
becoming a different there's new hybrid
species out there that's
androgynous so but it's good inshallah i
hope people
enjoy it he's he's a qigong master
and qigong is not a religious uh
exercise it there is relation to the
taoist tradition
and to shaolin temples and things like
that so so there are there is
association but it's
it's a it's the exercise that went with
martial arts in china
and it's very very uh
invigorating for people that do it on a
regular basis and practice it but he's
going to be working with you so you can
pretty much
learn how to do it during the time and
it's good to learn it from somebody
there's a lot online and things like
that
but according to the new york times the
longest living
human being ever was a qigong teacher in
china
they ascertained he claimed to be 235
years of age
but they did ascertain that he was at
least 170
and and he taught qigong to the imperial
troops and the new york times sent a
team over
to find out about him in 1932 i think so
that was actually
um and ate goji berries and
drank green tea and gensang
so i mean i don't know if anybody really
wants to
stick around here for 175 years but
but the time we're here we should try to
be as healthy as possible you know
because
it's it'll help you yeah
my mom was at the grocery store and you
know how they have those all those funny
national enquirer and all those and she
was my mom's 94
this year and she was there was another
old lady in the line
and she looked at my mother and then she
looked at the magazines and she said
aren't you glad we're on our way out
set up my nickel