David Hume
A Treatise of Human Nature (1739). Section IV: Of Personal Identity
Of Personal Identity
There are some philosophers, who imagine we are every moment
intimately conscious of what we call our SELF; that we feel its
existence and its continuance in existence; and are certain, beyond
the evidence of a demonstration, both of its perfect identity and
simplicity. The strongest sensation, the most violent passion,
say they, instead of distracting us from this view, only fix it
the more intensely, and make us consider their influence on self
either by their pain or pleasure. To attempt a farther proof of
this were to weaken its evidence; since no proof can be deriv'd
from any fact, of which we are so intimately conscious; nor is
there any thing, of which we can be certain, if we doubt of this.
Unluckily all these positive assertions are contrary to that
very experience, which is pleaded for them, nor have we any idea
of self, after the manner it is here explain'd. For from
what impression cou'd this idea be deriv'd? This question 'tis
impossible to answer without a manifest contradiction and absurdity;
and yet 'tis a question, which must necessarily be answer'd, if
we wou'd have the idea of self pass for clear and intelligible.
It must be some one impression, that gives rise to every real
idea. But self or person is not any one impression, but that to
which our several impressions and ideas are suppos'd to have a
reference. If any impression gives rise to the idea of self, that
impression must continue invariably the same, thro' the whole
course of our lives; since self is suppos'd to exist after that
manner. But there is no impression constant and invariable. Pain
and pleasure, grief and joy, passions and sensations succeed each
other, and never all exist at the same time. It cannot, therefore,
be from any of these impressions, or from any other, that the
idea of self is deriv'd; and consequently there is no such idea.
But farther, what must become of all our particular perceptions
upon this hypothesis? All these are different, and distinguishable,
and separable from each other, and may be separately consider'd,
and may exist separately, and have no need of any thing to support
their existence. After what manner, therefore, do they belong
to self; and how are they connected with it? For my part, when
I enter most intimately into what I call myself, I always
stumble on some particular perception or other, of heat or cold,
light or shade, love or hatred, pain or pleasure. I never can
catch myself at any time without a perception, and never
can observe any thing but the perception. When my perceptions
are remov'd for any time, as by sound sleep; so long am I insensible
of myself, and may truly be said not to exist. And were
all my perceptions remov'd by death, and cou'd I neither think,
nor feel, nor see, nor love, nor hate after the dissolution of
my body, I shou'd be entirely annihilated, nor do I conceive what
is farther requisite to make me a perfect non-entity. If any one,
upon serious and unprejudic'd reflection thinks he has a different
notion of himself, I must confess I can reason no longer
with him. All I can allow him is, that he may be in the right
as well as I, and that we are essentially different in this particular.
He may, perhaps, perceive something simple and continu'd, which
he calls himself; tho' I am certain there is no such principle
in me.
But setting aside some metaphysicians of this kind,. I may venture
to affirm of the rest of mankind, that they are nothing but a
bundle or collection of different perceptions, which succeed each
other with an inconceivable rapidity, and are in a perpetual flux
and movement. Our eyes cannot turn in their sockets without varying
our perceptions. Our thought is still more variable than our sight;
and all our other senses and faculties contribute to this change;
nor is there any single power of the soul, which remains unalterably
the same, perhaps for one moment. The mind is a kind of theatre,
where several perceptions successively make their appearance;
pass, re-pass, glide away, and mingle in an infinite variety of
postures and situations. There is properly no simplicity in
it at one time, nor identity in different; whatever natural propension
we may have to imagine that simplicity and identity. The comparison
of the theatre must not mislead us. They are the successive perceptions
only, that constitute the mind; nor have we the most distant
notion of the place, where these scenes are represented, or of
the materials, of which it is compos'd.
What then gives us so great a propension to ascribe an identity
to these successive perceptions, and to suppose ourselves possest
of an invariable and uninterrupted existence thro' the whole course
of our lives? In order to answer this question, we must distinguish
betwixt personal identity, as it regards our thought or imagination,
and as it regards our passions or the concern we take in ourselves.
The first is our present subject; and to explain it perfectly
we must take the matter pretty deep, and account for that identity,
which we attribute to plants and animals; there being a great
analogy betwixt it, and the identity of a self or person.
We have a distinct idea of an object, that remains invariable
and uninterrupted thro' a suppos'd variation of time; and this
idea we call that of identity or sameness. We have also a distinct
idea of several different objects existing in succession, and
connected together by a close relation; and this to an accurate
view affords as perfect a notion of diversity, as if there
was no manner of relation among the objects. But tho' these two
ideas of identity, and a succession of related objects be in themselves
perfectly distinct, and even contrary, yet 'tis certain, that
in our common way of thinking they are generally confounded with
each other. That action of the imagination, by which we consider
the uninterrupted and invariable object, and that by which we
reflect on the succession of related objects, are almost the same
to the feeling, nor is there much more effort of thought requir'd
in the latter case than in the former. The relation facilitates
the transition of the mind from one object to another, and renders
its passage as smooth as if it contemplated one continu'd object.
This resemblance is the cause of the confusion and mistake, and
makes us substitute the notion of identity, instead of that of
related objects. However at one instant we may consider the related
succession as variable or interrupted, we are sure the next to
ascribe to it a perfect identity, and regard it as enviable and
uninterrupted. Our propensity to this mistake is so great from the resemblance above-mention'd, that we fall into it
before we are aware; and tho' we incessantly correct ourselves
by reflection, and return to a more accurate method of thinking,
yet we cannot long sustain our philosophy, or take off this biass
from the imagination. Our last resource is to yield to it, and
boldly assert that these different related objects are in effect
the same, however interrupted and variable. In order to justify
to ourselves this absurdity, we often feign some new and unintelligible
principle, that connects the objects together, and prevents their
interruption or variation. Thus we feign the continu'd existence
of the perceptions of our senses, to remove the interruption:
and run into the notion of a soul, and self, and substance,
to disguise the variation. But we may farther observe, that where
we do not give rise to such a fiction, our propension to confound
identity with relation is so great, that we are apt to imagine[1]
something unknown and mysterious, connecting the parts, beside
their relation; and this I take to be the case with regard to
the identity we ascribe to plants and vegetables. And even when
this does not take place, we still feel a propensity to confound
these ideas, tho' we are not able fully to satisfy ourselves
in that particular, nor find any thing invariable and uninterrupted
to justify our notion of identity.
>[1] If the reader is desirous to see how a great genius may be influenc'd by these seemingly trivial principles of the imagination, as well as the mere vulgar, let him read my Lord Shaftsbury's reasonings concerning the uniting principle of the universe, and the identity of plants and animals. See his Moralists or Philosophical rhapsody .
Thus the controversy concerning identity is not merely a dispute
of words. For when we attribute identity, in an improper sense,
to variable or interrupted objects, our mistake is not confin'd
to the expression, but is commonly attended with a fiction, either
of something invariable and uninterrupted, or of something mysterious
and inexplicable, or at least with a propensity to such fictions.
What will suffice to prove this hypothesis to the satisfaction
of every fair enquirer, is to shew from daily experience and observation,
that the objects, which are variable or interrupted, and yet are
suppos'd to continue the same, are such only as consist of a succession
of parts, connected together by resemblance, contiguity, or causation.
For as such a succession answers evidently to our notion of diversity,
it can only be by mistake we ascribe to it an identity;
and as the relation of parts, which leads us into this mistake,
is really nothing but a quality, which produces an association
of ideas, and an easy transition of the imagination from one to
another, it can only be from the resemblance, which this act of
the mind bears to that, by which we contemplate one continu'd
object, that the error arises. Our chief business, then, must
be to prove, that all objects, to which we ascribe identity, without
observing their invariableness and uninterruptedness, are such
as consist of a succession of related objects.
In order to this, suppose any mass of matter, of which the parts
are contiguous and connected, to be plac'd before us; 'tis plain
we must attribute a perfect identity to this mass, provided all
the parts continue uninterruptedly and invariably the same, whatever
motion or change of place we may observe either in the whole or
in any of the parts. But supposing some very small or inconsiderable
part to be added to the mass, or subtracted from it; tho' this
absolutely destroys the identity of the whole, strictly speaking;
yet as we seldom think so accurately, we scruple not to pronounce
a mass of matter the same, where we find so trivial an alteration.
The passage of the thought from the object before the change to
the object after it, is so smooth and easy, that we scarce perceive
the transition, and are apt to imagine, that 'tis nothing but
a continu'd survey of the same object.
There is a very remarkable circumstance, that attends this experiment;
which is, that tho' the change of any considerable part in a mass
of matter destroys the identity of the whole, let we must measure
the greatness of the part, not absolutely, but by its proportion
to the whole. The addition or diminution of a mountain wou'd not
be sufficient to produce a diversity in a planet: tho' the change
of a very few inches wou'd be able to destroy the identity of
some bodies. 'Twill be impossible to account for this, but by
reflecting that objects operate upon the mind, and break or interrupt
the continuity of its actions not according to their real greatness,
but according to their proportion to each other: And therefore,
since this interruption makes an object cease to appear the same,
it must be the uninterrupted progress o the thought, which constitutes
the imperfect identity.
This may be confirm'd by another phenomenon. A change {1:538}
in any considerable part of a body destroys its identity; but
'tis remarkable, that where the change is produc'd gradually and
insensibly we are less apt to ascribe to it the same effect. The
reason can plainly be no other, than that the mind, in following
the successive changes of the body, feels an easy passage from
the surveying its condition in one moment to the viewing of it
in another, and at no particular time perceives any interruption
in its actions. From which continu'd perception, it ascribes a
continu'd existence and identity to the object.
But whatever precaution we may use in introducing the changes
gradually, and making them proportionable to the whole, 'tis certain,
that where the changes are at last observ'd to become considerable,
we make a scruple of ascribing identity to such different objects.
There is, however, another artifice, by which we may induce the
imagination to advance a step farther; and that is, by producing
a reference of the parts to each other, and a combination to some
common end or purpose. A ship, of which a considerable part has
been chang'd by frequent reparations, is still considered as the
same; nor does the difference of the materials hinder us from
ascribing an identity to it. The common end, in which the parts
conspire, is the same under all their variations, and affords
an easy transition of the imagination from one situation of the
body to another.
But this is still more remarkable, when we add a sympathy
of parts to their common end, and suppose that they bear to
each other, the reciprocal relation of cause and effect in all
their actions and operations. This is the case with all animals
and vegetables; where not only the several parts have a reference
to some general purpose, but also a mutual dependence on, and
connexion with each other. The effect of so strong a relation
is, that tho' every one must allow, that in a very few years both
vegetables and animals endure a total change, yet we still attribute
identity to them, while their form, size, and substance are entirely
alter'd. An oak, that grows from a small plant to a large tree,
is still the same oak; tho' there be not one particle of matter,
or figure of its parts the same. An infant becomes a man, and
is sometimes fat, sometimes lean, without any change in his identity.
We may also consider the two following phaenomena, which
are remarkable in their kind. The first is, that tho' we commonly
be able to distinguish pretty exactly betwixt numerical and specific
identity, yet it sometimes happens, that we confound them, and
in our thinking and reasoning employ the one for the other. Thus
a man, who hears a noise, that is frequently interrupted and renew'd,
says, it is still the same noise; tho' 'tis evident the sounds
have only a specific identity or resemblance, and there is nothing
numerically the same, but the cause, which produc'd them. In like
manner it may be said without breach of the propriety of language,
that such a church, which was formerly of brick, fell to ruin,
and that the parish rebuilt the same church of free-stone, and
according to modern architecture. Here neither the form nor materials
are the same, nor is there any thing common to the two objects,
but their relation to the inhabitants of the parish; and yet this
alone is sufficient to make us denominate them the same. But we
must observe, that in these cases the first object is in a manner
annihilated before the second comes into existence; by which means,
we are never presented in any one point of time with the idea
of difference and multiplicity: and for that reason are less scrupulous
in calling them the same.
Secondly, We may remark, that tho' in a succession of related
objects, it be in a manner requisite, that the change of parts
be not sudden nor entire, in order to preserve the identity, yet
where the objects are in their nature changeable and inconstant,
we admit of a more sudden transition, than wou'd otherwise be
consistent with that relation. Thus as the nature of a river consists
in the motion and change of parts; tho' in less than four and
twenty hours these be totally alter'd; this hinders not the river
from continuing the same during several ages. What is natural
and essential to any thing is, in a manner, expected; and what
is expected makes less impression, and appears of less moment,
than what is unusual and extraordinary. A considerable change
of the former kind seems really less to the imagination, than
the most trivial alteration of the latter; and by breaking less
the continuity of the thought, has less influence in destroying
the identity.
We now proceed to explain the nature of personal identity,
which has become so great a question in philosophy, especially
of late years in England, where all the abstruser
sciences are study'd with a peculiar ardour and application. And
here 'tis evident, the same method of reasoning must be continu'd.
which has so successfully explain'd the identity of plants, and
animals, and ships, and houses, and of all the compounded and
changeable productions either of art or nature. The identity,
which we ascribe to the mind of man, is only a fictitious one,
and of a like kind with that which we ascribe to vegetables and
animal bodies. It cannot, therefore, have a different origin,
but must proceed from a like operation of the imagination upon
like objects.
But lest this argument shou'd not convince the reader; tho' in
my opinion perfectly decisive; let him weigh the following reasoning,
which is still closer and more immediate. 'Tis evident, that the
identity, which we attribute to the human mind, however perfect
we may imagine it to be, is not able to run the several different
perceptions into one, and make them lose their characters of distinction
and difference, which are essential to them. 'Tis still true,
that every distinct perception, which enters into the composition
of the mind, is a distinct existence, and is different, and distinguishable,
and separable from every other perception, either contemporary
or successive. But, as, notwithstanding this distinction and separability,
we suppose the whole train of perceptions to be united by identity,
a question naturally arises concerning this relation of identity;
whether it be something that really binds our several perceptions
together, or only associates their ideas in the imagination. That
is, in other words, whether in pronouncing concerning the identity
of a person, we observe some real bond among his perceptions,
or only feel one among the ideas we form of them. This question
we might easily decide, if we wou'd recollect what has been already
prov'd at large, that the understanding never observes any real
connexion among objects, and that even the union of cause and
effect, when strictly examin'd, resolves itself into a customary
association of ideas. For from thence it evidently follows, that
identity is nothing really belonging to these different perceptions,
and uniting them together; but is merely a quality, which we attribute
to them, because of the union of their ideas in the imagination,
when we reflect upon them. Now the only qualities, which can give
ideas an union in the imagination, are these three relations
above-mention'd. These are the uniting principles in the ideal
world, and without them every distinct object is separable by
the mind, and may be separately considered, and appears not to
have any more connexion with any other object, than if disjoin'd
by the greatest difference and remoteness. 'Tis, therefore, on
some of these three relations of resemblance, contiguity and causation,
that identity depends; and as the very essence of these relations
consists in their producing an easy transition of ideas; it follows,
that our notions of personal identity, proceed entirely from the
smooth and uninterrupted progress of the thought along a train
of connected ideas, according to the principles above-explain'd.
The only question, therefore, which remains, is, by what relations
this uninterrupted progress of our thought is produc'd, when we
consider the successive existence of a mind or thinking person.
And here 'tis evident we must confine ourselves to resemblance
and causation, and must drop contiguity, which has little or no
influence in the present case.
To begin with resemblance; suppose we cou'd see clearly into
the breast of another, and observe that succession of perceptions,
which constitutes his mind or thinking principle, and suppose
that he always preserves the memory of a considerable part of
past perceptions; 'tis evident that nothing cou'd more contribute
to the bestowing a relation on this succession amidst all its
variations. For what is the memory but a faculty, by which we
raise up the images of past perceptions? And as an image necessarily
resembles its object, must not the frequent placing of these
resembling perceptions in the chain of thought, convey the imagination
more easily from one link to another, and make the whole seem
like the continuance of one object? In this particular, then,
the memory not only discovers the identity, but also contributes
to its production, by producing the relation of resemblance among
the perceptions. The case is the same whether we consider ourselves
or others.
As to causation; we may observe, that the true idea of the human
mind, is to consider it as a system of different perceptions or
different existences, which are link'd together by the relation
of cause and effect, and mutually produce, destroy, influence,
and modify each other. Our impressions give rise to their correspondent
ideas; and these ideas in their turn produce other impressions.
One thought chaces another, and draws after it a third, by which
it is expell'd in its turn. In this respect, I cannot compare
the soul more properly to any thing than to a republic or commonwealth,
in which the several members are united by the reciprocal ties
of government and subordination, and give rise to other persons,
who propagate the same republic in the incessant changes of its
parts. And as the same individual republic may not only change
its members, but also its laws and constitutions; in like manner
the same person may vary his character and disposition, as well
as his impressions and ideas, without losing his identity. Whatever
changes he endures, his several parts are still connected by the
relation of causation. And in this view our identity with regard
to the passions serves to corroborate that with regard to the
imagination, by the making our distant perceptions influence each
other, and by giving us a present concern for our past or future
pains or pleasures.
As a memory alone acquaints us with the continuance and extent
of this succession of perceptions, 'tis to be considered, upon
that account chiefly, as the source of personal identity. Had
we no memory, we never shou'd have any notion of causation, nor
consequently of that chain of causes and effects, which constitute
our self or person. But having once acquir'd this notion of causation
from the memory, we can extend the same chain of causes, and consequently
the identity of our persons beyond our memory, and can comprehend
times, and circumstances, and actions, which we have entirely
forgot, but suppose in general to have existed. For how few of
our past actions are there, of which we have any memory? Who can
tell me, for instance, what were his thoughts and actions on the
1st of January 1715, the 11th of March 1719, and the 3rd of August
1733? Or will he affirm, because he has entirely forgot the incidents
of these days, that the present self is not the same person with
the self of that time; and by that means overturn all the most
established notions of personal identity? In this view, therefore,
memory does not so much produce as discover personal
identity, by shewing us the relation of cause and effect among
our different perceptions. 'Twill be incumbent on those, who affirm
that memory produces entirely our personal identity, to give a
reason why we can thus extend our identity beyond our memory.
The whole of this doctrine leads us to a conclusion, which is
of great importance in the present affair, viz. that all the nice
and subtile questions concerning personal identity can never possibly
be decided, and are to be regarded rather as grammatical than as
philosophical difficulties. Identity depends on the relations
of ideas; and these relations produce identity, by means of that
easy transition they occasion. But as the relations, and the
easiness of the transition may diminish by insensible degrees,
we have no just standard, by which we can decide any dispute
concerning the time, when they acquire or lose a title to the
name of identity. All the disputes concerning the identity of
connected objects are merely verbal, except so far as the relation
of parts gives rise to some fiction or imaginary principle of
union, as we have already observed.