_Evidence demanded._--It were perhaps a sufficient answer to this question to reply, What _evidence_ have we, or can we have, that they _do_ deceive us? In the absence of all evidence to the contrary, is it not more reasonable to suppose that our perceptions correspond to realities, than that they are without foundation, uncaused, or caused by something not at all answering to the apparent object of perception; more reasonable to suppose that there is a real table or book answering to my perception of one, than that I have the perception while there is no such reality? It remains with those, then, who question and deny the validity of sense-perception, to show reasons for such denial. And this becomes the more imperative on them, inasmuch as they contradict the common belief and universal opinion of mankind--nay, what, in spite of all their arguments, is still, by their own confession, their own practical conviction and belief. _Evidence impossible._--But whence is this evidence to come? Where is it to be sought? How are we to prove that sense deceives us, except by arguments drawn from sense? And if sense is not reliable in the first instance, why rely upon it in the second, to prove that it is not reliable? If the senses do habitually deceive us, manifestly it can never be shown that they do. And, even if this could be shown, it would be impossible to find any thing better to rely upon in their stead. We have these guides or none. We have these instruments of observation provided for the voyage of life. We may pronounce them worthless and throw them into the sea, but we cannot replace them. _Inconsistent and contradictory Testimony of Sense._--But it may be replied that the testimony of sense is often inconsistent with itself, and contradictory of itself. What is sweet to one is sour and bitter to another. What seems a round tower in the distance becomes a square one as you approach; and the straight stick that you hold in your hand appears crooked when thrust into the water. There is in reality, however, no contradiction or inconsistency in the cases supposed. The change of circumstances accounts in every instance for the change of appearance. In the case of the stick, for example, the different density of the water accounts for the refraction of the rays of light that pass through it, and this accounts for the crooked appearance of the stick that is only partially submerged. So in the other cases; it is no contradiction that an object which appears round at a distance of ten miles, should appear square at the distance of so many rods--or that the taste of two persons should not agree as to the savor of a given object.