As an empiricist, John Locke looked to experience as the source of much or most of knowledge, and in some way, perhaps, the foundation of all knowledge. Yet Locke was aware of the complexities which arise when one uses this distinction in the careful analysis of knowledge.
There are relatively clear cut cases: The sense of vision may tell us that before us is a blueness; rational reflection may tell us that a = a. But between those extremes are a variety of borderline cases which are more complicated and do not always fall neatly into or or the other of those two categories.
One example is a perception which is the result of raw a posteriori sense-data which have been processed by a priori rational concepts, as J.L. Mackie explains:
The empiricist may, and Locke does, recognize that even the reception of ideas in perception is not wholly passive, but includes a considerable element of (unconscious) interpretation.
Locke shows how raw sense-data, which is a sensation and not yet a perception, needs to be processed by concepts in order to become a perception and eventually to become knowledge. A drawing on a two-dimensional paper of a three-dimensional object furnishes an example:
We are further to consider concerning perception, that the ideas we receive by sensation are often, in grown people, altered by the judgment, without our taking notice of it. When we set before our eyes a round globe of any uniform color, v.g. gold, alabaster, or jet, it is certain that the idea thereby imprinted on our mind is of a flat circle, variously shadowed, with several degrees of light and brightness coming to our eyes. But we having, by use, been accustomed to perceive what kind of appearance convex bodies are wont to make in us; what alterations are made in the reflections of light by the difference of the sensible figures of bodies; — the judgment presently, by an habitual custom, alters the appearances into their causes. So that from that which is truly variety of shadow or color, collecting the figure, it makes it pass for a mark of figure, and frames to itself the perception of a convex figure and an uniform color; when the idea we receive from thence is only a plane variously coloured, as is evident in painting.
There is a long series of thinkers in the history of philosophy who have written about this matter. Routinely, it is framed by some type of dichotomies: experience vs. reason, a priori vs. a posteriori, analytic vs. synthetic, etc.
As with any dichotomy, one may ask whether there are other alternatives in addition to the two given.
As William Uzgalis writes, “Locke claims that ideas are the materials of knowledge and all ideas come from experience.” Uzgalis is expressing the more-or-less standard understanding of Locke. It is worth noting that Locke, in most of his texts, hesitates to write that all knowledge comes from experience, but rather writes that all ideas come from experience: this nuance is worth noting.
In any case, however, another question presents itself: when Locke writes ‘experience,’ does he mean ‘sensory experience,’ i.e., from our five physical senses? Or does he leave room for some other types of experience?
Locke wrote about Paul, the author of several New Testament epistles, that Paul obtained something — ideas or knowledge — directly. Would Paul’s reception of propositions from God count as ‘experience’ for Locke? Locke writes:
Paul was miraculously called to the ministry of the gospel, and declared to be a chosen vessel; that he had the whole doctrine of the gospel from God, by immediate revelation; and was appointed to be the apostle of the Gentiles.
Even more direct, Locke uses the word ‘knowledge’ to refer to the content of Paul’s experience:
For his information in Christian knowledge, and the mysteries and depths of the dispensation of grace by Jesus Christ, God himself had condescended to be his instructor and teacher.
One could, then, begin to construct a paradigm with two categories of experience: first, the experience which arrives by means of the five physical senses; second, experience which arrives otherwise.
If there is such a thing as some type of experience distinct from physical experience, then what could it be? There might be more than one answer. Such non-sensory experiences could be emotional: experiencing happiness or sadness. They could be rational: the experience of calculating, for example. Locke speaks of ‘dictation’ to describe Paul’s experience: Locke says that Paul was “under the Spirit of God, that dictated these sacred writings.” Was this an audible dictation, i.e., the ordinary physical sense of hearing? Or was it somehow an experience of ideas: ideas arising without the five physical senses?
Rene DesCartes is often seen as the opposite of Locke, especially in terms of their respective epistemological systems. Locke however uses one of DesCartes’ more notorious vocabulary items when speaking of Paul’s experience. Cartesian scholars have long wrestled with how DesCartes uses the word ‘light,’ especially in the phrase ‘natural light’ or ‘light of nature.’ It seems to indicate, for DesCartes, an a priori bit of knowledge which is so obvious in its truth that it cannot be doubted. Critics of DesCartes accuse him of a deus ex machina move which begs the question of epistemological certainty when he invokes this natural light. Locke uses a similar phrase to describe the source of Paul’s knowledge:
He was full stored with knowledge of the things he treated of, for he had light from heaven, it was God himself furnished him.
As Locke uses the phrase ‘immediate revelation,’ so he also here speaks of a ‘truth’ which has been ‘revealed’ — truth being one of the usual ingredients of knowledge, as in ‘justified true belief.’
Like Francis’s Bacon’s listing of the sources of experimental error, Locke also indicates that human perception is liable to error, and proposes reliance on revelation as one possible measure against such error:
We are all men, liable to errors, and infected with them; but have this sure way to preserve ourselves, every one, from danger by them, if, laying aside sloth, carelessness, prejudice, party, and a reverence of men, we betake ourselves, in earnest, to the study of the way to salvation, in those holy writings, wherein God has revealed it from heaven, and proposed it to the world, seeking our religion, where we are sure it is in truth to be found, comparing spiritual things with spiritual things.
John Locke’s epistemology, then, may have room for something more than the usual ‘experience vs. reason’ template to describe sources of ideas, of perceptions, and of knowledge. Or, at least, if he does limit the sources to those two, then he may be broadening the definitions of ‘reason’ and ‘experience’ to include more than one might at first suppose.
