The things which the principle of design does not explain are many and serious.  Some are in their nature inexplicable, at least are beyond the power and province of science.  Others are of matters which scientific students have to consider, and upon which they may form opinions, more or less well grounded.  As to biological science—­with which alone we are concerned—­it is getting to be generally thought that this principle, as commonly understood, is weighted with much more than it can carry.

This statement will not be thought exaggerated by those most familiar with the facts and the ideas of the age, and accustomed to look them in the face.  Design is held to, no doubt, by most, and by a sure instinct; not, however, as always offering an explanation of the facts, but in spite of the failure to do so.  The stumbling-blocks are various, and they lie in every path:  we can allude only to one or two as specimens.

Adaptation and utility are the marks of design.  What, then, are organs not adapted to use marks of?  Functionless organs of some sort are the heritage of almost every species.  We have ways of seeming to account for them—­and of late one which may really account for them—­but they are unaccountable on the principle of design.  Some, shutting their eyes to the difficulty, deny that we know them to be functionless, and prefer to believe they must have a use because they exist, and are more or less connected with organs which are correlated to obvious use; but only blindfolded persons care to tread the round of so narrow a circle.  Of late some such abortive organs in flowers and fruits are found to have a use, though not the use of their kind.  But unwavering believers in design should not trust too much to instances of this sort.  There is an old adage that, if anything be kept long enough, a use will be found for it.  If the following up of this line, when it comes in our way, should bring us round again to a teleological principle, it will not be one which conforms to the prevalent ideas now attacked.

It is commonly said that abortive and useless organs exist for the sake of symmetry, or as parts of a plan.  To say this, and stop there, is a fine instance of mere seeming to say something.  For, under the principle of design, what is the sense of introducing useless parts into a useful organism, and what shadow of explanation does “symmetry” give?  To go further and explain the cause of the symmetry and how abortive organs came to be, is more to the purpose, but it introduces quite another principle than that of design.  The difficulty recurs in a somewhat different form when an organ is useful and of exquisite perfection in some species, but functionless in another.  An organ, such as an eye, strikes us by its exquisite and, as we may, perfect adaptation and utility in some animal; it is found repeated, still useful but destitute of many of its adaptations, in some animal of lower grade; in some one lower still it is rudimentary and useless.  It is asked, If the first was so created for its obvious and actual use, and the second for such use as it has, what was the design of the third?  One more case, in which use after all is well subserved, we cite from the article already much quoted from: