Letters from Dr. J. G. in defence of his Essay on the difference of the relation between motive and action, and that of cause and effect in physics: with replies by A. Crombie

Preface

. It is proper to acquaint the reader with the circumstances, which have given occasion to the following letters. In the year 1792, Dr. Gregory presented to the public an Essay in two volumes 8VO,1 in which he assumed the merit of disproving the doctrine of Philosophical Necessity by Mathema tical evidence. His reasoning appeared to me wholly fallacious ; and in an Essay, in defence of this doctrine, published about a year afterwards, I endeavoured to demonstrate the invalidity of 1 Dr. G., in his first Letter, has called his work, An Essay on the difference between the relation of motive and action and that of cause and effect in physics. The title is correct and appropriate. I have therefore, in order to prevent misconception, ventured to adopt it, in preference to that which appears in the title page of the work itself, namely, Essays Philosophi cal and Literary, from which it would naturally be concluded, that there arc several Essays, and these also on a diversity of subjects.

Let. b VI his argument; and, at the same time, took the liberty to reprehend the insolence, and the illiberality, with which he treated his opponents. Soon after the publication of my Essay, I was informed, that it was Dr. Gregory s intention to reply to my strictures ; and that I had reason to expect a severe retort, for my animadversions on his work. Neither pleased, nor alarmed, at this information, I waited two or three years, in expectation of Dr. Gregory 's reply ; and at last concluded from his silence, either that he had relinquished his intention, or that my information must have been incorrect. My conclusion, however, was erroneous. After the lapse of ten years, I received, in the month of October 1803, the first letter of the following series, accompanied with a short communication, informing me, that his Answer to my animadversions was nearly ready for the press, and that, as soon as the Session of College was over, I might expect to see it in print ; unless my reply to his first letter should convince him of the justness of my reasoning, or the invalidity of his own.

He assured me at the same time, that, if I could point out any fallacy in his argument, his intended publication should be suppressed, that his error should be acknowleged, and that I should have his per mission to make that acknowlegement public. He requested also to know, whether I chose to have the remainder of the letters transmitted to me "seri " atim? or all together. My reply, dated in January 1804, with a few additions and alterations, is here submitted to the judgment of the reader. It was ac companied with a communication, expressing my desire to avail myself of his offer, and to receive the remaining letters, either individually or collect ively, as he might prefer. I had reason, therefore* to expect,, that these letters would be sent to me, agreeably to Dr. Gregory s voluntary promise.

I had reason likewise to expect, either that the whole would be published in the ensuing spring, or that he would acknowlege his argument to be fallacious. My expectations however were disappointed. Neither were the remaining letters transmitted to me, nor did Dr. Gregory publish his Defence, nor did he acknowlege himself in any error, or retract his argument. Conceiving myself justified in re quiring an explanation of this extraordinary procedure, but unwilling to urge him to any precipitate determination, I suffered five years more to elapse, and Dr. Gregory was still silent ; nor was I favoured with a perusal of the remainder of his Defence. Of this conduct I found it difficult even to conjecture any satisfactory explanation, without resorting to the very unfavourable suspicion, that my reply to his first letter had convinced him of his error, but that he wanted the candour and magnanimity to acknowlege it If he was persuaded, that his argument was demonstrative, and his Defence unanswerable, it is to be presumed, that, with this conviction, he would have published his letters, as he gave me reason to expect.

If, on the contrary, he was con vinced, that his reasoning was fallacious, and that his arguments were refuted by my first letter, it became his duty, in conformity to his express promise, candidly and explicitly to acknowlege his error. On either supposition his conduct appeared irreconcileable with his engagements, as either clearly implied or positively expressed. I took the liberty, therefore, in a letter, dated in March 1809, to remind him of his promise, and requested to be informed, whether he intended to publish his Defence, or retract his argument. In answer, I received six letters, and part of a seventh, all printed, accompanied with a pretty long epistle, giving me full permission to publish all, or any part, of these letters, in answer to my strictures ; assuring me, at the same time, of his " hearty " inclination to proceed."

It appeared to me, and perhaps may appear to the reader, somewhat ex traordinary, that a work, which, the author had signified, was nearly ready for the press, and might be expected to appear in six months, and of which, after the expiration of these six months 208 pages were actually printed, could not be completed in five years afterwards, making every allowance for the interruptions occasioned by professional engagements, which few can feel more sensibly than myself. Having finished my replies to these letters, I informed Dr. Gregory, that, as he had neither published his answer, nor retracted his opinion, one or other of which alternatives he had given me reason to expect, it was my intention to avail my self of his permission to publish his letters with my Replies. To this intimation I was favoured X with an answer, in which he requested, that I would either transmit to him the manuscript, before it was sent to the printer, or the proof sheets, one after another, as they proceeded from the press.

The former alternative, for obvious reasons, was to be preferred; a manuscript copy was accordingly sent to him, with an assurance, that I should have pleasure in correcting any error or mis-statement, into which I might inadvertently have fallen, and in giving him an opportunity of making any alteration, either in the matter, or the manner, of his Defence, which he might deem necessary. Dr. Gregory has been in possession of my Replies for nearly five years, during which time he has observed an entire silence. I am, therefore, it is conceived, warranted in concluding, that he considers his letters to be a full and satisfactory answer to my animadversions. For, if my replies have convinced him, that his argument is fallacious, and that he erred in impeaching the veracity of his opponents, it can scarcely be supposed, that he is so devoid of all candour, as well as of that sacred regard, which is due by every man to an express and voluntary promise, as not to acknowlege that his reasoning is false, and that his treatment of Necessarians is illiberal and unjust.

Nay, if he has discovered, that his letters are not a valid and satisfactory reply, but believes, that he is still capable of offering a complete justification of his reasoning and his conduct, it may, on this supposition, be fairly presumed, that he would have revoked his permission to publish his Defence, and requested me to wait for a farther communication. Nor is it unreasonable to presume, that the space of five years, during which time my Replies have been in his possession, would have amply sufficed for this purpose. If Dr. Gregory should proceed, of which I entertain no sanguine expectation, his future observations, if not composed of irrelevant matter, or of groundless or frivolous complaints, shall receive from me every possible attention. In the mean time, the following letters will suffice to exhibit the nature of his argument, and the character of his Defence, of the validity of which the reader will judge. A.C. FROM DR. GREGORY.