.
Lock
observes
,
'That we get the Idea of Time, or Duration, by reflecting on that Train of Ideas which succeed one another in our Minds: That for this Reason, when we sleep soundly without dreaming, we have no Perception of Time, or the Length of it whilst we sleep; and that the Moment wherein we leave off to think, till the Moment we begin to think again, seems to have no distance.'
To which the Author adds,
'And so I doubt not but it would be to a waking Man, if it were possible for him to keep only one Idea in his Mind, without Variation, and the Succession of others: And we see, that one who fixes his Thoughts very intently on one thing, so as to take but little notice of the Succession of Ideas that pass in his Mind whilst he is taken up with that earnest Contemplation, lets slip out of his Account a good Part of that Duration, and thinks that Time shorter than it is.'
We might carry this Thought further, and consider a Man as, on one Side, shortening his Time by thinking on nothing, or but a few things; so, on the other, as lengthening it, by employing his Thoughts on many Subjects, or by entertaining a quick and constant Succession of Ideas.