The two views very unequally divide the scientific world; so that believers in “the divine right of majorities” need not hesitate which side to take, at least for the present.  Up to a time within the memory of a generation still on the stage, two hypotheses about the nature of light very unequally divided the scientific world.  But the small minority has already prevailed:  the emission theory has gone out; the undulatory or wave theory, after some fluctuation, has reached high tide, and is now the pervading, the fully established system.  There was an intervening time during which most physicists held their opinions in suspense.

The adoption of the undulatory theory of light called for the extension of the same theory to heat, electricity, and magnetism, and this promptly suggested the hypothesis of a correlation, material connection, and transmutability of heat, light, electricity, magnetism, etc.; which hypothesis the physicists held in absolute suspense until very lately, but are now generally adopting.  If not already established as a system, it promises soon to become so.  At least, it is generally received as a tenable and probably true hypothesis.

Parallel to this, however less cogent the reasons, Darwin and others, having shown it likely that some varieties of plants or animals have diverged in time into cognate species, or into forms as different as species, are led to infer that all species of a genus may have thus diverged from a common stock, and thence to suppose a higher community of origin in ages still farther back, and so on.  Following the safe example of the physicists, and acknowledging the fact of the diversification of a once homogeneous species into varieties, we may receive the theory of the evolution of these into species, even while for the present we hold the hypothesis of a further evolution in cool suspense or in grave suspicion.  In respect to very many questions a wise man’s mind rests long in a state neither of belief nor of unbelief.  But your intellectually short-sighted people are apt to be preternaturally clear-sighted, and to find their way very plain to positive conclusions upon one side or the other of every mooted question.

In fact, most people, and some philosophers, refuse to hold questions in abeyance, however incompetent they may be to decide them.  And, curiously enough, the more difficult, recondite, and perplexing the questions or hypotheses are, such, for instance, as those about organic Nature, the more impatient they are of suspense.  Sometimes, and evidently in the present case, this impatience grows out of a fear that a new hypothesis may endanger cherished and most important beliefs.  Impatience under such circumstances is not unnatural, though perhaps needless, and, if so, unwise.