aspects, Sensibility, Understanding, and Reason. The à priori forms of Sensibility, which rendered Experience possible, were Space and Time: these were forms of thought, conditions of cognition. It was by such forms of thought that he reoccupied the position taken by Leibnitz in defending and amending the doctrine of innate ideas, namely, that knowledge has another source besides sensible experience—the intellectus ipse.

While, therefore, any one who spoke of space as a 'form of the understanding' would certainly use language which Kant would have disclaimed, Kant himself would have been surprised to hear that space was not held by him as a form of thought.' January 3. GEORGE HENRY LEWES.

THE following paragraphs, I believe, faithfully render sundry passages of Kant's writings :

'Objects are given to us by means of sense (Sinnlichkeit), which is the sole source of intuitions (Anschauungen); but they are thought by the understanding, from which arise conceptions (Begriffe).' ('Kritik,' p. 55, Hartenstein's edition.)

'The understanding is the faculty of thought. Thought is knowledge by means of conception.' (Ibid. p. 93.)

'The original consciousness of space is an intuition à priori, and not a conception (Begriff).' (Ibid. p. 60.)

'Space is nothing else than the form of all the phenomena of the external senses; that is, it is the subjective condition of sense, under which alone external intuition is possible for us.' (Ibid. p. 61.)

'Our nature is such, that intuition can never be otherwise than sensual (sinnlich); that is, it only contains the modes in which we are affected by objects. On the other hand, the power of thinking the object of sensual intuition, is the understanding. Neither of these faculties is superior to the other. Without sense, no object would be given us, and without understanding none would be thought. Thoughts without contents are empty, intuitions without conceptions (Begriffe) are blind.' (Ibid. p. 82.)

'Time and space are mere forms of sense (Formen unserer Sinnlichkeit, 'Prolegomena,' p. 33) and 'mere forms of intuition.' ('Kritik,' p. 76.)

With these passages before one, there can be no doubt that that thorough and acute student of Kant, Dr. Ingleby, was perfectly right when he said that Kant would have repudiated the affirmation that 'space is a form of thought.' For in these sentences, and in many others which might be cited, Kant expressly lays down the doctrine that thought is the work of the understanding, intuition of the sense; and that space, like time, is an intuition. The only 'forms of thought' in Kant's sense, are the categories. T. H. HUXLEY.

January 14.

Do not believe Professor Sylvester has been betrayed, as Mr. G. H. Lewes asserts, into any misconception of this matter by me.

When Kant, at the outset, says, 'Alles Denken aber muss sich, es sei geradezu oder im Umschweife, vermittelst gewisser Merkmale, zuletzt auf Anschauungen...beziehen,' it would take the veriest dunderhead not to see that all forms of intuition must be, indirectly at least, forms of thought. I never dreamed of disputing so obvious a position. But I object to the phrase, 'forms of thought,' as designating Space and Time, on the ground of precision. They are peculiarly forms of general Sense, and not forms of Thought as Thought. Kant, I believe, eschewed the phrase in that sense, and, for all I see, might for the same reason have disclaimed it. C. M. INGLEBY.

Ilford, Jan. 14.

It is not my habit' when objections are made to what I have written, silently to correct my error or silently disregard the criticism.' If the objections are well founded, I think it due to the cause of truth to make a frank confession of error, and in the opposite case to reply to the objections.

With reference, then, to Mr. Lewes's strictures in Nature's

last number, I beg to say that Dr. Ingleby has betrayed' me into no error. If I have fallen into error, it is with my eyes open, and after satisfying myself by study of Kant, that to speak of Space and Time, whether as forms of understanding, or as forms of thought, is an unauthorised and misleading mode of expression. Space and Time are forms of sensitivity or intuition. The categories of Kant (so essentially in this point differing from those of Aristotle) do not contain Space and Time among them, and are properly called forms of understanding or thought.

To the existence of thought the operation of the understanding is a necessary preliminary.

Sensibility and intuition are antecedent to any such operation. Can Mr. Lewes point to any passage in Kant where Space and Time are designated forms of thought? I shall indeed be surprised if he can do so-as much surprised as if Mr. Todhunter or Mr. Routh, in their Mechanical Treatises, were to treat energy and force as convertible terms. To such a misuse of the word energy it would be little to the point to urge that force without energy is a mere potential tendency. It is just as little to the point in the matter at issue, for Mr. Lewes to inform the readers of Nature that intuition without thought is mere sensuous impression.

Dr. Ingleby has rendered, in my opinion, a very great service to the English reading public, by drawing attention to so serious and prevalent an error as that of confounding the categories (the proper forms of thought as thought) with Space and Time, the forms of intuition, the sentinels, so to say, who keep watch and ward outside the gates of the Understanding.

Athenaeum Club, Jan. 15.

J. J. SYLVESTER.

ALTHOUGH I do not feel myself called upon to modify in the least what was said in my former letter on this subject, the three letters which appear to-day in answer to it are too important to be left unnoticed.

The case is briefly this: In the History of Philosophy' I had

to expound Kant's doctrine, and to criticise it, not only in itself, but in reference to the great question of the origin of knowledge. In the pages of exposition I uniformly speak of Space and Time as forms of Intuition; no language can be plainer. I also mark the distinction between Sensibility and Understanding, as that of Intuition and Thought. After enumerating the Categories, I add, In those Categories Kant finds the pure forms of the Understanding. They render Thought possible.'

But when, ceasing to expound the system, I had to criticise it, and especially to consider it in reference to the great question; there was no longer any need to adhere to a mode of expression which would have been obscure and misleading. I therefore uniformly class Space and Time among the forms of Thought, connecting them with the doctrine of Necessary Truths and Fundamental Ideas, which, according to the à priori school, are furnished ready-made-brought by the Mind as its native dowry, not evolved in it through Experience.

Now the question is, Have I put language into Kant's mouth which he would disclaim, or is such language misleading? That Kant would have said the language was not what he had employed, I freely admit; but that he would have disclaimed it as misrepresenting his meaning, I deny. I was not bound to follow his language when the task of exposition was at an end; but only bound not to translate his opinions into language which would distort them.

In classing Space and Time among the Forms of Thought, I classed them beside the Categories of the Understanding and the Ideas of Reason, i.e. the purely intellectual conditions existing à priori in the Mind. The Mind is said by Kant to be endowed with three faculties-Sensibility, Understanding, and Reason. The activity of the Mind is threefold-Intuitive Thought, Conceptive or Discursive Thought, and Regulative Thought. There could not be an equivoque in my using the word Thought in its ordinary philosophical acceptation as expressive of all mental activity whatever, exclusive of mere sensation; although Kant assigns a more restricted meaning in his technical use of the word, i.e. what we call Logic. And that Kant meant nothing

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opposed to the ordinary interpretation is obvious. It is obvious because, as I said in my former letter, Intuition without Thought is mere sensuous impression. Mr. Sylvester demurs to this, so I will show it in a single citation :-'In the transcendental Aesthetic,' says Kant, we will first isolate Sensibility by separating from it all that the Understanding through its concepts thinks therewith, so that nothing but empirical Intuition remains. Secondly, we will lop off from this empirical Intuition everything relating to sensation (Empfindung); so that thereby nothing will remain but pure Intuition and the mere form of phenomena, which is the one thing that Sensibility can furnish à priori. By this investigation it will appear that there are two pure forms of sensuous Intuition which are à priori principles of Cognition.' ('Kritik,' § 1, ed. Hartenstein, p. 61.)

Mr. Sylvester correctly says, that Intuition and Thought are not convertible terms. But he is incorrect in assuming that they differ as potential and actual; they differ as species and genus; therefore, whatever is a form of Intuition, though not a form of Logic, must be a form of Thought; unless intuitive Thought be denied altogether. How little Kant denied it is evident in every section of his work. In asserting that Space and Time as Intuitions belong to the subjective constitution of the Mind-subjectiven Beschaffenheit unseres Gemüths (p. 62)— he expresses this; but it is unequivocally expressed in the following definition:-'A perception, when it refers solely to the subject, as a modification of its states, is sensation, an objective perception is cognition: this is either Intuition or Concept, "intuitus vel conceptus." ('Kritik,' p. 294.) Is not thought implied in cognition? Again:-'The proposition "I think" is an undetermined empirical Intuition, i.e. Perception consequently, it proves that Sensation, which belongs to Sensibility, must lie at the basis of this proposition. . . . I do not mean thereby that the "I" in the "I think" is an empirical representation (Vorstellung), on the contrary, it is purely intellectual, because it belongs to thought in general. But without some empirical representation which would give Thought its material there could be no such act of Thought as the "I think", (p. 324, note).

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