Locke on Judgment, Faith, Reason, Etc.
(Essay, Book IV)

Early Modern Philosophy

On some themes from Book IV. I'll begin with a couple of issues about knowledge, then continue on to Locke's remarks about things we can't have knowledge of but can still have some reasonable degree of assurance about.

I. The Reality of Knowledge

Locke occasionally addresses general skeptical worries of the kind Descartes introduces in Meditation I, though he never seems to take them too seriously. One of his more detailed discussions is in his of "the reality of knowledge" (IV.iv).

The problem stems from Locke's idea that all of our knowledge is of the relations of ideas. This naturally suggests the question: "But what if all of our ideas are entirely disconnected from reality? What if the real world is nothing like our idea of it?"

Locke concedes that we want more than just knowledge of how ideas relate to each other: we also want knowledge of how they relate to the real world. "Our knowledge therefore is real, only so far as there is a conformity between our ideas and the reality of things" (IV.iv.3).

Locke thinks that much of our knowledge is of general propositions. These are conditional in nature. That is, I can know that every triangle has angles that sum to 180 even if I don't know whether there actually are any triangles in reality: what I know is that everything is such that, if it is a triangle, its angles sum to 180. Similarly, Locke says that I can know that "murder deserves death" without knowing whether there actually are any murders: what I know is that if one person murders another, he or she deserves to die (IV.iv.8).

Notice how similar Locke's points about general knowledge are to Descartes' discussion in Meditation V, in which he says that we can know about the essence of material objects without knowing whether any such objects actually exist.

II. Knowledge of Existence

Another context in which it is clear that Locke thinks we can have knowledge about the relation between ideas and reality, not merely about relations of ideas, occurs in his discussion of our knowledge of the existence of particular things.

Locke thinks we have intuitive knowledge of our own existence, demonstrative knowledge of the existence of God, and sensitive knowledge of the existence of particular things that we are currently experiencing or have experienced in the past. Beyond that, we don't have any knowledge of existence.

III. Knowledge and Judgment: An Outline

Knowledge (requires certainty: e.g. IV.iii.14)

intuitive (IV.ii.1)
demonstrative (IV.ii.2)
sensitive (IV.ii.14)

Judgment (= probable opinion).

of things of which we can have experience (grounds: experience and testimony, IV.xv.4)

assurance -- sense experience and testimony completely agree (IV.xvi.6)
confidence -- sense experience and testimony generally agree (IV.xvi.77)
unavoidability -- we have testimony only (IV.xvi.8)
lower degrees of belief -- testimony, experience disagree (IV.xvi.9)
    belief, doubt, wavering, distrust, etc.

of things we can't have experience of (because too small or too remote) -- here we use analogy (IV.xvi.12)

examples: heat = molecular motion, color = reflectance properties, existence of higher beings between us and God

IV. Reason

Reason is the process of making inferences. Some kinds of knowledge (or judgment) require reason, and some don't.

Intuitive knowledge is direct and does not involve reasoning (IV.xvii.14).

Demonstration involves certain inferences from certain starting points, so it does involve reasoning (IV.xvii.15).

Sensitive knowledge seems to be direct: if I see that there is an object in front of me, I don't need to make an inference.

"Probable reasoning" doesn't give us knowledge (certainty), but otherwise it's very similar to demonstration

There's a nice pattern here:

  direct indirect
more certain (about ideas only?) intuition demonstration
less certain (about the external world?) sensation probable reasoning

V. Faith

Where does faith fit in in the knowledge and judgment outline in section III above?

Definition: "Faith . . . is the assent to any proposition, not . . . made out by the deductions of reason; but upon the credit of the proposer, as coming from GOD, in some extraordinary way of communication. This way of discovering truths to men we call revelation" (IV.xviii.2).

Revelation appears to be a variety of what Locke calls testimony. So it doesn't seem to be opposed to judgment, but rather to be a form of judgment or probable opinion. However, it doesn't seem to fit anywhere in the outline very neatly since it (a) involves testimony, but (b) also concerns things we can't have direct experience of.

Locke's most important point (I think): "It still belongs to reason, to judge of the truth of its being a revelation, and of the signification of the words, wherein it is delivered" (IV.xviii.8; L makes a similar point in section 10).

Last update: March 18, 2009. 
Curtis BrownClassical Modern PhilosophyPhilosophy Department | Trinity University