Let us leave for the present, in its native shadows, the central point of our own self; the original centre of our earliest apparent universe. Yet, if we cannot _know_ this first growing-point of our individual life, it may be useful to inquire what can we know _about_ it? can we learn, for example, how that inner vitality, once begun, is maintained and fed?--By a process of receiving into itself, (we are told), the aliment which flows through our senses. We are also told, (as appeared in the last chapter), how very requisite is a knowledge of _natural_ processes. Let us, then, look at this process of sense-alimentation, narrowing the problem as much as possible. We have already cut off _one_ end of it--the germ-point of the _self_-stimulated; and will now cut off _another_ piece--the assimilation of mental ideas when elaborated. We simply ask how does this food from without, get _into_ us? The widest avenue of entrance is proverbially our sense of eyesight. Its information, (as people in general agree, from Horace down to Mr. Mill), being gathered through many definite impressions, and received from all distances, is at once the most significant, and the most commanding. The first step is clear. We see by impinging rays of light,--movements in a luminiferous ether, making images on the sensitive network of the eye; a circumstance ascertained by the same sense of sight which receives the image. From this delicate surface, begins a second series of movements;--they take place this time in an organized nerve-material, and are carried, like telegraph-currents, to the Sensory. Arrived there, we may next suppose that they excite some new motions, or corpuscular changes. Do we know--_can_ we know any more? Is the grammar or dictionary written which translates them into the language of the mind; or teaches us how we have, since our infancy, worked a perpetual miracle of speech respecting each of them? The eye, as an optical instrument,[v] is a marvel of science displayed; the eye as an instrument of intelligence, especially of human intelligence, is a marvel of inscrutable mystery. The mysteries of every-day life are the last things dreamed of in every-day philosophy. When we wake up to their existence, it is astonishing to find how continually, without being able to explain things, we can feel, and know them;--know them that is in the sense of acting intelligently (without theorizing) upon them.