As for John Locke, he reveals in the “Epistle to the Reader,” which stands as a preface to the “Essay,” the critical spirit in which his work was taken up.  “Were it fit to trouble thee,” he writes, “with the history of this Essay, I should tell thee, that five or six friends meeting at my chamber, and discoursing on a subject very remote from this, found themselves quickly at a stand, by the difficulties that rose on every side.  After we had a while puzzled ourselves, without coming any nearer a resolution of those doubts which perplexed us, it came into my thoughts, that we took a wrong course; and that before we set ourselves upon inquiries of that nature, it was necessary to examine our own abilities, and to see what objects our understandings were, or were not, fitted to deal with.”

This problem, proposed by himself to his little circle of friends, Locke attacked with earnestness, and as a result he brought out many years later the work which has since become so famous.  The book is literally a critique of the reason, although a very different critique from that worked out by Kant.

“If, by this inquiry into the nature of the understanding,” says Locke, “I can discover the powers thereof, how far they reach, to what things they are in any degree proportionate, and where they fail us; I suppose it may be of use to prevail with the busy mind of man to be more cautious in meddling with things exceeding its comprehension; to stop when it is at the utmost extent of its tether; and to sit down in a quiet ignorance of those things which upon examination are found to be beyond the reach of our capacities.” [2]

To the difficulties of the task our author is fully alive:  “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.  But whatever be the difficulties that lie in the way of this inquiry, whatever it be that keeps us so much in the dark to ourselves, sure I am that all the light we can let in upon our own minds, all the acquaintance we can make with our own understandings, will not only be very pleasant, but bring us great advantage, in directing our thoughts in the search, of other things.” [3]

(2) Thus, many men have attempted to produce a critical philosophy, and in much the same sense as that in which Kant uses the words.  Those who have come after them have decided that they were not sufficiently critical, that they have made unjustifiable assumptions.  When we come to read Kant, we will, if we have read the history of philosophy with profit, not forget to ask ourselves if he has not sinned in the same way.

For example, we will ask;—­

(a) Was Kant right in maintaining that we find in experience synthetic judgments (section 51) that are not founded upon experience, but yield such information as is beyond the reach of the empiricist?  There are those who think that the judgments to which he alludes in evidence of his contention—­the mathematical, for instance—­are not of this character.