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this could not be done, and that I must reconstruct what I had written. I was at work on this—to which I hope to return shortly—when Dr. Krause's " Erasmus Darwin," with its preliminary notice by Mr. Charles Darwin, came out, and having been compelled, as I have shown above, by Dr. Krause's work to look a little into the German language, the opportunity seemed favourable for going on with it and becoming acquainted with Professor Hering's lecture. I therefore began to translate his lecture at once, with the kind assistance of friends whose patience seemed inexhaustible, and found myself well rewarded for my trouble.

Professor Hering and I, to use a metaphor of his own, are as men who have observed the action of living beings upon the stage of the world, he from the point of view at once of a spectator and of one who has free access to much of what goes on behind the scenes, I from that of a spectator only, with none but the vaguest notion of the actual manner in which the stage machinery is worked. If two men so placed, after years of reflection, arrive independently of one another at an identical conclusion as regards the manner in which this machinery must have been invented and perfected, it is


natural that each should take a deep interest in the arguments of the other, and be anxious to put them forward with the utmost possible prominence. It seems to me that the theory which Professor Hering and I are supporting in common, is one the importance of which is hardly inferior to that of the theory of evolution itself —for it puts the backbone, as it were, into the theory of evolution. I shall therefore make no apology for laying my translation of Professor Hering's work before my reader.

Concerning the identity of the main idea put forward in " Life and Habit" with that of Professor Hering's lecture, there can hardly, I think, be two opinions. We both of us maintain that we grow our limbs as we do, and possess the instincts we possess, because we remember having grown our limbs in this way, and having had these instincts in past generations when we were in the persons of our forefathers—each individual life adding a small (but so small, in any one lifetime, as to be hardly appreciable) amount of new experience to the general store of memory; that we have thus got into certain habits which we can now rarely break; and that we do much of what we do unconsciously on the same principle as that (whatever it is) on which we do all other habitual actions with the greater ease and unconsciousness the more often we repeat them. Not only is the main idea the same, but I was surprised to find how often Professor Hering and I had taken the same illustrations with which to point our meaning.

Nevertheless, we have each of us left undealt with some points which the other has treated of. Professor Hering, for example, goes into the question of what memory is, and this I did not venture to do. I confined myself to saying that whatever memory was, heredity was also. Professor Hering adds that memory is due to vibrations of the molecules of the nerve fibres, which under certain circumstances recur, and bring about a corresponding recurrence of visible action.

This approaches closely to the theory concerning the physics of memory which has been most generally adopted since the time of Bonnet, who wrote as follows :—

"The soul never has a new sensation but by the interposition of the senses. This sensation has been originally attached to the motion of certain fibres. Its reproduction or recollection by the senses will then be likewise connected with these same fibres." 1 . . .

1 "Contemplation of Nature," Engl, trans., Lond. 1776. Preface p. xxxvi.

And again :—

"It appeared to me that since this memory is connected with the body, it must depend upon some change which must happen to the primitive state of the sensible fibres by the action of objects. I have, therefore, admitted as probable that the state of the fibres on which ah object has acted is not precisely the same after this action as it was before. I have conjectured that the sensible fibres experience more or less durable modifications, which constitute the physics of memory and recollection." 1 . . .

Professor Hering comes near to endorsing this view, and uses it for the purpose of explaining personal identity. This, at least, is what he does in fact, though perhaps hardly in words. I did not say more upon the essence of personality than that it was inseparable from the idea that the various phases of our existence should have flowed one out of the other, "in what we see as a continuous, though it may be at times a very troubled, stream ; "2 but I maintained that the identity between two successive generations was of essentially the same kind as that existing, between an infant and an octogenarian. I thus left personal identity unexplained, though insisting that it was the key to two apparently distinct sets of

1 "Contemplation of Nature," Engl, trans., Lond. 1766. Preface, p. xxxviii.

2 Life and Habit, p. 97. .

phenomena, the one of which had been hitherto considered incompatible with our ideas concerning it. Professor Hering insists on this too, but he gives us farther insight into what personal identity is, and explains how it is that the phenomena of heredity are phenomena also of personal identity.

He implies, though in the short space at his command he has hardly said so in express terms, that personal identity as we commonly think of it—that is to say, as confined to the single life of the individual—consists in the uninterruptedness of a sufficient number of vibrations, which have been communicated from molecule to molecule of the nerve fibres, and which go on communicating each one of them its own peculiar characteristic elements to the new matter which we introduce into the body by way of nutrition. These vibrations may be so gentle as to be imperceptible for years together; but they are there, and may become perceived if they receive accession through the running into them of a wave going the same way as themselves, which wave has been set up in the ether by exterior objects and has been communicated to the organs of sense.

As these pages are on the point of leaving my hands, I see the following remarkable pas

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