'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（异种的） 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（前情） -- 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.'

Moxon was silent for a long time, gazing absently into the fire. It was growing late and I thought it time to be going, but somehow I did not like the notion of leaving him in that isolated house, all alone except for the presence of some person of whose nature my conjectures（推测，猜想） could go no further than that it was unfriendly, perhaps malign（诽谤，污蔑） . Leaning toward him and looking earnestly into his eyes while making a motion with my hand through the door of his workshop, I said:

'Moxon, whom have you in there?'