Hypothesis may be noticed here as being a species of _embryo_ experiment. Hypothesis is guessing at the truth. It is a conjecture or supposition relating to the cause of an effect. It imagines that where certain conditions exist, the desired result will ensue. But all these conjectures must be founded on observation. For, in the wildest conjecture, unless made by a madman, there is some reason. Hypothesis is incipient truth founded on a few facts which make it probable, but not on sufficient to make it certain. Hypothesis does not directly discover truth, but it is a guide to experiment, which does. The hypotheses of Columbus respecting an unknown continent, did not of itself discover America--but it directed the experiment of his voyage there, which did. To hypothesise alone is the error of the visionary and the dreamer. Practical wisdom, as far as possible, tests hypothesis by experiment. Sir C. Bell conjectured that the nervous fluid of the human body was analogous to galvanic fluid, and then, by experiments on various animals, he endeavoured to test his hypothesis. However, great thinkers arise who are best employed in contriving plans for others to execute--in telling others what they are to do. Great poets belong to this class. They are often incapable of the concentrated labour of furnishing proofs of their hypothesis. Gladly should we recognise the mission of such men. They work for humanity by thinking for humanity. 'All who think,' says Lytton, 'are co-operative with all who work.' Labour supplies our wants, thought teaches us dominion over nature. Labour is but the means of subsistence, it is thought that makes it the source of wealth by multiplying its powers. To the value of hypothesis Mr. Mill bears this testimony, that by suggesting observations and experiments, it puts us upon the road to, independent evidence, if it be really attainable, and till it be attained, the hypothesis ought not to count for more than a suspicion. The function of hypothesis is one which must be reckoned absolutely indispensable in science. Without such assumption, science would not have attained its present state. Nearly everything which is now theory was once hypothesis.* * Logic, Vol. II, p. 18.