Before man can feel pleasure or pain from outward objects or from thoughts, he must perceive them. To a new-born infant, or a blind person enabled to see for the first time, objects before the eyes can hardly be said to exist. The blue sky and a green tree beside a white house are not seen but as a blotch of colours which touches the eye. This is the account given by persons couched for cataract, who have never before seen a ray of light. They see as if they saw not. But the power is in them. By degrees they receive the images, and perceive the objects. A child learns to receive sounds separately; then to perceive one voice among others; then to distinguish one tone from another--the voice of soothing from that of playfulness--the tone of warning from that of approbation; then it receives thoughts through the sounds; and so on, till the power is exercised to the fullest extent that we know of--when distinct ideas are admitted from the minutest appearances or leadings--strange bodies detected in the heavens, and fresh truths in the loftiest regions of human speculation. It depends much on training whether objects and thoughts remain for life indistinct and confused before the perceptive power, as before infant vision, or whether all is clear and vivid as before a keen and practised eye.
We know not how Memory acts, any more than we understand how we feel pleasure and pain. But we all know how the power of recalling images, words, thoughts, and feelings, depends on exercise. A person whose power of memory has been neglected has little use of his past life. The time, and people, and events that have passed by have left him little better than they found him: while every day, every person, and every incident deposits some wealth of knowledge with him whose memory can receive and retain his experience.
Then there are other powers which it will be enough merely to mention here, as we shall have to consider them more fully hereafter. Man has the power, after perceiving objects and thoughts, to compare them, and see when they differ and agree; to penetrate their nature, and understand their purpose and action. It is thus that he obtains a knowledge of creation, and the curious powers, whether hidden or open to view, which are for ever at work in it.