It is not easy for a man to begin to think; but when once he has begun he will never leave off.  Once a thinker, always a thinker, and the understanding once practised in reflection will never rest.  You may therefore think that I do too much or too little; that the human mind is not by nature so quick to unfold; and that after having given it opportunities it has not got, I keep it too long confined within a circle of ideas which it ought to have outgrown.

But remember, in the first place, that when I want to train a natural man, I do not want to make him a savage and to send him back to the woods, but that living in the whirl of social life it is enough that he should not let himself be carried away by the passions and prejudices of men; let him see with his eyes and feel with his heart, let him own no sway but that of reason.  Under these conditions it is plain that many things will strike him; the oft-recurring feelings which affect him, the different ways of satisfying his real needs, must give him many ideas he would not otherwise have acquired or would only have acquired much later.  The natural progress of the mind is quickened but not reversed.  The same man who would remain stupid in the forests should become wise and reasonable in towns, if he were merely a spectator in them.  Nothing is better fitted to make one wise than the sight of follies we do not share, and even if we share them, we still learn, provided we are not the dupe of our follies and provided we do not bring to them the same mistakes as the others.

Consider also that while our faculties are confined to the things of sense, we offer scarcely any hold to the abstractions of philosophy or to purely intellectual ideas.  To attain to these we require either to free ourselves from the body to which we are so strongly bound, or to proceed step by step in a slow and gradual course, or else to leap across the intervening space with a gigantic bound of which no child is capable, one for which grown men even require many steps hewn on purpose for them; but I find it very difficult to see how you propose to construct such steps.

The Incomprehensible embraces all, he gives its motion to the earth, and shapes the system of all creatures, but our eyes cannot see him nor can our hands search him out, he evades the efforts of our senses; we behold the work, but the workman is hidden from our eyes.  It is no small matter to know that he exists, and when we have got so far, and when we ask.  What is he?  Where is he? our mind is overwhelmed, we lose ourselves, we know not what to think.

Locke would have us begin with the study of spirits and go on to that of bodies.  This is the method of superstition, prejudice, and error; it is not the method of nature, nor even that of well-ordered reason; it is to learn to see by shutting our eyes.  We must have studied bodies long enough before we can form any true idea of spirits, or even suspect that there are such beings.  The contrary practice merely puts materialism on a firmer footing.