488 fR A OMENTS F SCTENCE. 
by no means easy to combat such notions. For when I 
say " I see you," and that there is not the least doubt 
about it, the obvious reply is, that what I am really con- 
scious of is an affection of my own retina. And if I urge 
that my sight can be checked by touching you, the retort 
would be that I am equally transgressing the limits of fact; 
for what I am really conscious of is, not that you are 
there, but that the nerves of my hand have undergone a 
change. All we hear, and see, and touch, and taste, and 
smell, are, it would be urged, mere variations of our own 
condition, beyond which, even to the extent of a hair's 
breadth, we cannot go. That anything answering to our 
impressions exists outside of ourselves is not 'A fact, but 
an inference, to which all validity would be denied by an 
idealist like Berkeley, or by a skeptic like Hume. Mr. 
Spencer takes another line. With him, as with the 
uneducated man, there is no doubt or question as to the 
existence of an external world. But he differs from the 
uneducated, who think that the world really is what con- 
sciousness represents it to be. Our states of consciousness 
are mere symbols of an outside entity which produces them 
and determines the order of their succession, but the real 
nature of which we can never know.* In fact, the whole 
process of evolution is the manifestation of a Power 
absolutely inscrutable to the intellect of man. As little in 
our day as in the days of Job can man by searching find 
this Power out. Considered fundamentally, then, it is by 
the operation of an insoluble mystery that life on earth is 
evolved, species differentiated,' and mind unfolded, from 
their prepotent elements in the immeasurable past. 
* In a paper, at once popular and profound, entitled "Recent 
Progress in the Theory of Vision," contained in the volume of lec- 
tures by Heimholtz, published by Longmans, this symbolism of our 
states of consciousness is also dwelt upon. The impressions of sense 
are the mere signs of external things. In this paper Heimholtz con- 
tends strongly against the view that the consciousness of space is 
inborn; and he evidently doubts the power of the chick to pick up 
grains of corn without preliminary lessons. On this point, he says, 
further experiments are needed. Such experiments have been since 
made by Mr. Spalding, aided, I believe, in some of his observations 
by the accomplished and deeply lamented Lady Amberly; and they 
seem to prove conclusively that the chick does not need a single 
moment's tuition to enable it to stand, run, govern the muscles of its 
eyes, and peck. Heimholtz, however, is contending against the 
notion of pre-established harmony; and I am not aware of his views 
as to the organization of experiences of race or breed. 
