known properties of man; that is, if those properties have nothing in them that is abfolutely incompatible with one another, we fhall be obliged to conclude (unless we openly violate the rules of philofophizing) that no other kind of fubftance enters into his compofition; the fuppofition being manifeftly unnecessary, in order to account for any appear

ance whatever.

All the properties that have hitherto been attributed to matter, may be comprized under thofe of attraction and repulfion (all the effects of which have been fhewn to be produced by powers, independent of all folidity) and of extenfion, by means of which matter occupies a certain portion of space. Befides these properties, man is poffeffed of the powers of fenfation or perception, and thought. But if, without giving the reins to our imaginations, we fuffer ourselves to be guided in our inquiries by the simple rules of philofophizing above mentioned, we must neceffarily conclude, as it appears to me, that thefe powers also may belong to the fame fubftance, that has alfo the properties of attraction, repulfion, and extenfion, which I, as well as others, call by the name of matter; though I have been obliged to divest it of one property which has hitherto been thought effential to it, as well as to give it others which have not been thought effential to it; and confequently my idea of this fubftance is

not,

not, in all respects, the fame with that of other metaphyficians.

The reason of the conclufion above mentioned, is fimply this, that the powers of fenfation or perception, and thought, as belonging to man, have never been found but in conjunction with a certain organized fyftem of matter; and therefore, that thofe powers neceffarily exist in, and depend upon, fuch a fyftem. This, at leaft, must be our conclufion, till it can be shewn that these powers are incompatible with other known properties of the fame fubftance; and for this I fee no fort of pretence.

It is true, that we have a very imperfect idea of what the power of perception is, and it may be as naturally impoffible that we should have a clear idea of it, as that the eye fhould fee itself. But this very ignorance ought to make us cautious in afferting with what other properties it may, or may not, exist. Nothing but a precife and definite knowledge of the nature of perception and thought can authorize any perfon to affirm, whether they may not belong to an extended fubftance, which has also the properties of attraction and repulfion. Seeing, therefore, no fort of reason to imagine that thefe different properties are really inconfiftent, any more than the different properties of refiftance and extenfion, I am, of course, under the neceffity of being guided by the phenomena in my conclu

fions concerning the proper feat of the powers of perception and thought. These phenomena I shall now briefly represent.

Had we formed a judgement concerning the necessary feat of thought, by the circumftances that univerfally accompany it, which is our rule in all other cafes, we could not but have concluded, that in man it is a property of the nervous fyftem, or rather of the brain. Because, as far as we can judge, the faculty of thinking, and a certain state of the brain, always accompany and correfpond to one another; which is the very reason why we believe that any property is inherent in any substance whatever. There is no inftance of any man retaining the faculty of thinking, when his brain was destroyed; and whenever that faculty is impeded, or injured, there is fufficient reafon to believe that the brain is disordered in proportion; and therefore we are neceffarily led to confider the latter as the feat of the former.

Moreover, as the faculty of thinking in general ripens, and comes to maturity with the body, it is alfo obferved to decay with it; and if, in fome cafes, the mental faculties continue vigorous when the body in general is enfeebled, it is evidently because, in thofe particular cafes, the brain is not much affected by the general cause of weaknefs. But, on the other hand, if the brain alone be affected, as by a blow on the head, by actual preffure within the fkull, by fleep,

Or

or by inflammation, the mental faculties are univerfally affected in proportion.

Likewife, as the mind is affected in confequence of the affections of the body and brain, fo the body is liable to be reciprocally affected by the affections of the mind, as is evident in the vifible effects of all ftrong paffions, hope or fear, love or anger, joy or forrow, exultation or defpair. Thefe are certainly irrefragable arguments that it is properly no other than one and the fame thing that is fubject to thefe affections, and that they are neceffarily dependent upon one another. In fact, there is juft the fame reason to conclude, that the powers of fenfation and thought are the necessary result of a particular organization, as that found is the neceffary result of a particular concuffion of the air. For in both cafes equally the one conftantly accompanies the other, and there is not in nature a stronger argument for a necessary connection of any caufe and any effect.

To adopt an opinion different from this, is to form an hypothefis without a fingle fact to fupport it. And to conclude, as fome have done, that a material fyftem is fo far from being a neceffary pre-requifite to the faculty of thinking, that it is an obftruction to it, is to adopt a method of argumentation the very reverse of every thing that has hitherto been followed in philofophy. It is to conclude, not only without, but directly contrary to all appearances whatfoever.

That

That the perfection of thinking fhould depend on the found ftate of the body and brain in this life, infomuch that a man has no power of thinking without it, and to fuppofe him capable of thinking better when the body and brain are destroyed, feems to be the most unphilofophical and abfurd of all conclufions. If death be an advantage with refpect to thinking, difeafe ought to ought to be a propor-" tional advantage likewife; and univerfally, the nearer the body approaches to a state of diffolution, the freer and lefs embarraffed might the faculties of the mind be expected to be found. But this is the very reverse of what really happens.

Part of this argument is fo well represented, and fo forcibly urged, by the excellent Mr. Hallet, that I fhall quote the entire paffage from the first volume of his Difcourfes, p. 213.

"I see a man move, and hear him speak "for fome years. From his speech I certainly infer that he thinks, as I do. I fee "then that man is a being who thinks and "acts. After fome time the man falls down "in my fight, grows cold and ftiff. He "fpeaks and acts no more. Is it not then "natural to conclude that he thinks no more? "As the only reason I had to believe that he "did think was his motion and fpeech, fo

now that this motion and fpeech ceafe, I "have loft the only way of proving that he "had a power of thought.

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