A Treatise Concerning the Principles of Human Knowledge | Page 3

it to arise from the natural dulness and limitation of our
faculties. And surely it is a work well deserving our pains to make a
strict inquiry concerning the First Principles of Human Knowledge, to
sift and examine them on all sides, especially since there may be some
grounds to suspect that those lets and difficulties, which stay and
embarrass the mind in its search after truth, do not spring from any
darkness and intricacy in the objects, or natural defect in the
understanding, so much as from false Principles which have been
insisted on, and might have been avoided.
5. How difficult and discouraging soever this attempt may seem, when

I consider how many great and extraordinary men have gone before me
in the like designs, yet I am not without some hopes--upon the
consideration that the largest views are not always the clearest, and that
he who is short--sighted will be obliged to draw the object nearer, and
may, perhaps, by a close and narrow survey, discern that which had
escaped far better eyes.
6. A CHIEF SOURCE OF ERROR IN ALL PARTS OF
KNOWLEDGE.--In order to prepare the mind of the reader for the
easier conceiving what follows, it is proper to premise somewhat, by
way of Introduction, concerning the nature and abuse of Language. But
the unravelling this matter leads me in some measure to anticipate my
design, by taking notice of what seems to have had a chief part in
rendering speculation intricate and perplexed, and to have occasioned
innumerable errors and difficulties in almost all parts of knowledge.
And that is the opinion that the mind has a power of framing
ABSTRACT IDEAS or notions of things. He who is not a perfect
stranger to the writings and disputes of philosophers must needs
acknowledge that no small part of them are spent about abstract ideas.
These are in a more especial manner thought to be the object of those
sciences which go by the name of LOGIC and METAPHYSICS, and of
all that which passes under the notion of the most abstracted and
sublime learning, in all which one shall scarce find any question
handled in such a manner as does not suppose their existence in the
mind, and that it is well acquainted with them.
7. PROPER ACCEPTATION OF ABSTRACTION.--It is agreed on all
hands that the qualities or modes of things do never REALLY EXIST
EACH OF THEM APART BY ITSELF, and separated from all others,
but are mixed, as it were, and blended together, several in the same
object. But, we are told, the mind being able to consider each quality
singly, or abstracted from those other qualities with which it is united,
does by that means frame to itself abstract ideas. For example, there is
perceived by sight an object extended, coloured, and moved: this mixed
or compound idea the mind resolving into its simple, constituent parts,
and viewing each by itself, exclusive of the rest, does frame the abstract
ideas of extension, colour, and motion. Not that it is possible for colour

or motion to exist without extension; but only that the mind can frame
to itself by ABSTRACTION the idea of colour exclusive of extension,
and of motion exclusive of both colour and extension.
8. OF GENERALIZING [Note].--Again, the mind having observed that
in the particular extensions perceived by sense there is something
COMMON and alike IN ALL, and some other things peculiar, as this
or that figure or magnitude, which distinguish them one from another;
it considers apart or singles out by itself that which is common, making
thereof a most abstract idea of extension, which is neither line, surface,
nor solid, nor has any figure or magnitude, but is an idea entirely
prescinded from all these. So likewise the mind, by leaving out of the
particular colours perceived by sense that which distinguishes them one
from another, and retaining that only which is COMMON TO ALL,
makes an idea of colour in abstract which is neither red, nor blue, nor
white, nor any other determinate colour. And, in like manner, by
considering motion abstractedly not only from the body moved, but
likewise from the figure it describes, and all particular directions and
velocities, the abstract idea of motion is framed; which equally
corresponds to all particular motions whatsoever that may be perceived
by sense.
[Note: Vide Reid, on the Intellectual Powers of Man, Essay V, chap iii.
sec. 1, edit. 1843]
9. OF COMPOUNDING.--And as the mind frames to itself abstract
ideas of qualities or MODES, so does it, by the same precision or
mental separation, attain abstract ideas of the more compounded
BEINGS which include several coexistent qualities. For example, the
mind having observed that Peter, James, and John resemble each other
in certain common agreements of