'Do you happen to recall Herbert Spencer's definition of "life"? I read it thirty years ago. He may have altered it afterward¹, 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 heterogeneous²（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 phenomena³, 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 legitimate⁴ quarry⁵: 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 isolated⁶ house, all alone except for the presence of some person of whose nature my conjectures⁷（推测，猜想） could go no further than that it was unfriendly, perhaps malign⁸（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?'