any one else should be in there, and my interest in my friend—­ with doubtless a touch of unwarrantable curiosity—­led me to listen intently, though, I am happy to say, not at the keyhole.  There were confused sounds, as of a struggle or scuffle; the floor shook.  I distinctly heard hard breathing and a hoarse whisper which said “Damn you!” Then all was silent, and presently Moxon reappeared and said, with a rather sorry smile: 

“Pardon me for leaving you so abruptly.  I have a machine in there that lost its temper and cut up rough.”

Fixing my eyes steadily upon his left cheek, which was traversed by four parallel excoriations showing blood, I said: 

“How would it do to trim its nails?”

I could have spared myself the jest; he gave it no attention, but seated himself in the chair that he had left and resumed the interrupted monologue as if nothing had occurred: 

“Doubtless you do not hold with those (I need not name them to a man of your reading) who have taught that all matter is sentient, that every atom is a living, feeling, conscious being. I do.  There is no such thing as dead, inert matter:  it is all alive; all instinct with force, actual and potential; all sensitive to the same forces in its environment and susceptible to the contagion of higher and subtler ones residing in such superior organisms as it may be brought into relation with, as those of man when he is fashioning it into an instrument of his will.  It absorbs something of his intelligence and purpose—­more of them in proportion to the complexity of the resulting machine and that of its work.

“Do you happen to recall Herbert Spencer’s definition of ‘Life’?  I read it thirty years ago.  He may have altered it afterward, for anything I know, but in all that time I have been unable to think of a single word that could profitably be changed or added or removed.  It seems to me not only the best definition, but the only possible one.

“‘Life,’ he says, ’is a definite combination of heterogeneous changes, both simultaneous and successive, in correspondence with external coexistences and sequences.’”

“That defines the phenomenon,” I said, “but gives no hint of its cause.”

“That,” he replied, “is all that any definition can do.  As Mill points out, we know nothing of cause except as an antecedent—­nothing of effect except as a consequent.  Of certain phenomena, one never occurs without another, which is dissimilar:  the first in point of time we call cause, the second, effect.  One who had many times seen a rabbit pursued by a dog, and had never seen rabbits and dogs otherwise, would think the rabbit the cause of the dog.

“But I fear,” he added, laughing naturally enough, “that my rabbit is leading me a long way from the track of my legitimate quarry:  I’m indulging in the pleasure of the chase for its own sake.  What I want you to observe is that in Herbert Spencer’s definition of ‘life’ the activity of a machine is included—­there is nothing in the definition that is not applicable to it.  According to this sharpest of observers and deepest of thinkers, if a man during his period of activity is alive, so is a machine when in operation.  As an inventor and constructor of machines I know that to be true.”