Locke at the outset adopts a computational approach, rejecting the materialist
(he will not "meddle with the physical consideration of the mind") and
the theological (he will not speculate "wherein its essence consists"):
his concern is with "the original [origin], certainty, and extent of human
knowledge, together with the grounds and degrees of belief, opinion, and
assent" (1). By "knowledge" he means the ability to know, the faculty of
gathering and utilizing information; to understand its "extent" is significant
because it can lead men to realize what they cannot know, and thus "to
sit down in a quiet ignorance of those things which, upon examination,
are found to be beyond the reach of our capacities" (2). More generally,
we should "entertain all objects in that way and proportion that they are
suited to our faculties" (3). Holding out the hope that we will learn the
proper use of our limited capacities and specifically human faculties by
seeing "to what things they were adapted" (4), Locke is looking for what
we might call the computational specifications, the design of the human
mind.[1]

The arguments against innate
ideas

Situating himself against the rationalists, Locke begins by challenging
the "established opinion among some men, that there are in the understanding
certain innate principles" (12). In the following, I focus exclusively
on the arguments against epistemic rationalism, leaving aside the highly
interesting claims of ethical rationalism for the moment. Based on a model
of the understanding as a set of propositions present to consciousness
consisting in impressions on an unstructured substrate, he demonstrates
convincingly there are no innate ideas present from birth.

The assumption of cognitive transparency

Cognition, in Locke's view, consists in ideas, by which is meant "nothing
but the immediate objects of our minds in thinking" (6)--the common-sense
assumption that consciousness is the mind, that all cognition takes place
at the site of phenomenological awareness. True, Locke himself remarks
in the opening paragraph, "The understanding, like the eye, whilst it makes
us see and perceive all other things, takes no notice of itself; and it
requires art and pains to set it at a distance, and make it its own object"
(1); however, the assumption that what is needed is careful introspection
remains.

The metaphor of the wax tablet

Once cognitive transparency is assumed, the conscious content of the
mind becomes the test of innate ideas, "for to imprint anything on the
mind, without the mind's perceiving it, seems to me hardly intelligible"
(13). In this metaphor, the assumption that the clay itself has no structure
is already implied; the search for prior structure limits itself naturally
to conscious impressions.

The understanding as a set of propositions

In a related move, the understanding is tacitly equated with the conscious
product of understanding—knowledge, conceived as a set of propositions.
This makes the claim of cognitive transparency seem more plausible; it
is only common sense to hold that "No proposition can be said to be in
the mind which it never yet knew, which it was never yet conscious of."
(13). If you can die without realizing you know something, "this great
point will amount to nothing more, but only to a very improper way of speaking"
which in practice "says nothing different from those who deny innate principles"
(14).

Innate ideas as fully present at
birth

The innate ideas Locke argues against are those which "the soul receives
in its very first being, and brings into the world with it" (12). A simple
test of the rationalist hypothesis is thus to inquire into the ideas of
"children and idiots"; if it is granted that they have souls, it follows
that these should be impressed with innate ideas. Since it is simple to
ascertain that children do not have certain ideas-- such that the proposition
that "it is impossible for the same thing to be, and not to be" (13)--by
asking them, or by appealing to common knowledge of children, the presence
of innate ideas can swiftly be ruled out.

Summary

Locke’s critique of rationalism flows coherently from his underlying
assumptions of the understanding as

a set of propositions

present to consciousness

consisting in impressions on an unstructured substrate.

Within this framework, the rationalist claim is that innate ideas are universally
present at birth can be rejected as false.

Discussion

It is Locke’s assumptions rather than his explicit reasoning that is
problematic. These form a cluster; the notion that the understanding is
a product rather than a process follows from the common-sense assumption
of cognitive transparency, since it is precisely the products of cognition,
rather than its inferential processes, that are made available to consciousness.
Locke’s achievement lies in the computational approach itself: what he
establishes is the possiblility of thinking about the mind as an information
processor. Since the operation of the mind’s faculties are typically unavailable
to introspection, the assumption of cognitive transparency makes the rationalist
position, particularly in Locke’s formulation, untenable at the outset.

What Locke is unable to get at within the framework of these assumptions
is a conception of a specified faculty. It strikes him as self-evident
that humans have a general capacity to acquire propositions, but this fact
should be clearly distinguished from the claim of innate ideas (14).

The commonsense assumption of cognitive transparancy is not challenged
until Hume, whose introspective experiments begin to push past the limits
of conscious awareness. This simultaneously undermines the notion that
the understanding is a product, consisting in propositions; rather, it
is a process, where the power of making inferences (Hume’s celebrated Problem
of Induction) requires an explanation. It is the search for this explanation
that leads Kant to a formulation of transcendental categories.

1. By "adapted", Locke means "suited" in a general sense; the coincidence
with the terminology of evolution is of course accidental, and the notion
of design, if he felt it needed an explanation, would receive one from
theology. [Back]

Works
Cited

Page numbers are currently to the Promethean Books edition; I'll
change that to the edition listed in the bibliography.