I again remind the reader that there are all sorts of rationalists, in the philosophical sense of the word.  Some trust the power of the unaided reason without reserve.  Thus Spinoza, the pantheist, made the magnificent but misguided attempt to deduce the whole system of things physical and things mental from what he called the attributes of God, Extension and Thought.

On the other hand, one may be a good deal of an empiricist, and yet something of a rationalist, too.  Thus Professor Strong, in his recent brilliant book, “Why the Mind has a Body,” maintains that we know intuitively that other minds than our own exist; know it without gathering our information from experience, and without having to establish the fact in any way.  This seems, at least, akin to the doctrine of the “natural light,” and yet no one can say that Professor Strong does not, in general, believe in a philosophy of observation and experiment.

61.  EMPIRICISM.—­I suppose every one who has done some reading in the history of philosophy will, if his mother tongue be English, think of the name of John Locke when empiricism is mentioned.

Locke, in his “Essay concerning Human Understanding,” undertakes “to inquire into the original, certainty, and extent of human knowledge, together with the grounds and degrees of belief, opinion, and assent.”  His sober and cautious work, which was first published in 1690, was peculiarly English in character; and the spirit which it exemplifies animates also Locke’s famous successors, George Berkeley (1684-1753), David Hume (1711-1776), and John Stuart Mill (1806-1873).  Although Locke was a realist, Berkeley an idealist, Hume a skeptic, and Mill what has been called a sensationalist; yet all were empiricists of a sort, and emphasized the necessity of founding our knowledge upon experience.

Now, Locke was familiar with the writings of Descartes, whose work he admired, but whose rationalism offended him.  The first book of the “Essay” is devoted to the proof that there are in the mind of man no “innate ideas” and no “innate principles.”  That is to say, Locke tries to show that one must not seek, in the “natural light” to which Descartes turned, a distinct and independent source of information,

“Let us, then,” he continues, “suppose the mind to be, as we say, white paper, void of all characters, without any ideas; how comes it to be furnished?  Whence comes it by that vast store which the busy and boundless fancy of man has painted on it, with an almost endless variety?  Whence has it all the materials of reason and knowledge?  To this I answer in one word, from experience; in that all our knowledge is founded, and from that it ultimately derives itself.  Our observation, employed either about external sensible objects, or about the internal operations of our minds, perceived and reflected on by ourselves, is that which supplies our understandings with all the materials of thinking.  These two are the fountains of knowledge, from whence all the ideas we have, or can naturally have, do spring.” [1]