It is said that from early childhood the Redskins of Canada, train their sense of smell to such a degree of subtlety that, although they have dogs, they do not condescend to use them in hunting—­they are their own dogs.  Indeed I believe that if children were trained to scent their dinner as a dog scents game, their sense of smell might be nearly as perfect; but I see no very real advantage to be derived from this sense, except by teaching the child to observe the relation between smell and taste.  Nature has taken care to. compel us to learn these relations.  She has made the exercise of the latter sense practically inseparable from that of the former, by placing their organs close together, and by providing, in the mouth, a direct pathway between them, so that we taste nothing without smelling it too.  Only I would not have these natural relations disturbed in order to deceive the child, e.g.; to conceal the taste of medicine with an aromatic odour, for the discord between the senses is too great for deception, the more active sense overpowers. the other, the medicine is just as distasteful, and this disagreeable association extends to every sensation experienced at the time; so the slightest of these sensations recalls the rest to his imagination and a very pleasant perfume is for him only a nasty smell; thus our foolish precautions increase the sum total of his unpleasant sensations at the cost of his pleasant sensations.

In the following books I have still to speak of the training of a sort of sixth sense, called common-sense, not so much because it is common to all men, but because it results from the well-regulated use of the other five, and teaches the nature of things by the sum-total of their external aspects.  So this sixth sense has no special organ, it has its seat in the brain, and its sensations which are purely internal are called percepts or ideas.  The number of these ideas is the measure of our knowledge; exactness of thought depends on their clearness and precision; the art of comparing them one with another is called human reason.  Thus what I call the reasoning of the senses, or the reasoning of the child, consists in the formation of simple ideas through the associated experience of several sensations; what I call the reasoning of the intellect, consists in the formation, of complex ideas through the association of several simple ideas.

If my method is indeed that of nature, and if I am not mistaken in the application of that method, we have led our pupil through the region of sensation to the bounds of the child’s reasoning; the first step we take beyond these bounds must be the step of a man.  But before we make this fresh advance, let us glance back for a moment at the path we have hitherto followed.  Every age, every station in life, has a perfection, a ripeness, of its own.  We have often heard the phrase “a grown man;” but we will consider “a grown child.”  This will be a new experience and none the less pleasing.