A mind nourished on anatomical study is of course permeated with the suggestion of the vagueness and instability of biological species.  A biological species is quite obviously a great number of unique individuals which is separable from other biological species only by the fact that an enormous number of other linking individuals are inaccessible in time—­are in other words dead and gone—­and each new individual in that species does, in the distinction of its own individuality, break away in however infinitesimal degree from the previous average properties of the species.  There is no property of any species, even the properties that constitute the specific definition, that is not a matter of more or less.

If, for example, as species be distinguished by a single large red spot on the back, you will find if you go over a great number of specimens that red spot shrinking here to nothing, expanding there to a more general redness, weakening to pink, deepening to russet and brown, shading into crimson, and so on and so on.  And this is true not only of biological species.  It is true of the mineral specimens constituting a mineral species, and I remember as a constant refrain in the lectures of Professor Judd upon rock classification, the words, “they pass into one another by insensible gradations.”  It is true, I hold, of all things.

You will think perhaps of atoms of the elements as instances of identically similar things, but these are things not of experience but of theory, and there is not a phenomenon in chemistry that is not equally well explained on the supposition that it is merely the immense quantities of atoms necessarily taken in any experiment that masks by the operation of the law of averages the fact that each atom also has its unique quality, its special individual difference.

This ideal of uniqueness in all individuals is not only true of the classifications of material science; it is true and still more evidently true of the species of common thought; it is true of common terms.  Take the word “Chair.”  When one says chair, one thinks vaguely of an average chair.  But collect individual instances; think of armchairs and reading-chairs and dining-room chairs, and kitchen chairs, chairs that pass into benches, chairs that cross the boundary and become settees, dentist’s chairs, thrones, opera stalls, seats of all sorts, those miraculous fungoid growths that cumber the floor of the Arts and Crafts exhibition, and you will perceive what a lax bundle in fact is this simple straightforward term.  In co-operation with an intelligent joiner I would undertake to defeat any definition of chair or chairishness that you gave me.  Chairs just as much as individual organisms, just as much as mineral and rock specimens, are unique things—­if you know them well enough you will find an individual difference even in a set of machine-made chairs—­and it is only because we do not possess minds of unlimited capacity, because our brain has only a limited number of pigeon-holes for our correspondence with an unlimited universe of objective uniques, that we have to delude ourselves into the belief that there is a chairishness in this species common to and distinctive of all chairs.