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Biology ) as much as may be known of Man . In an inner centre closely , nay , inseparably connected with both , stands Chemistry , or the science of molecular action . Thus is the circle complete . I need scarcely saythat all such divisions are arbitrary . Nature admits of no distinct lines of demarcation . You cannot say , here ends the inorganic world , and here begins the organic j you cannot say , here we see the vegetable domain cease , and here the animal commence $ but you can and do say , this rose is a plant , this lion is an animal . Therefore , although Chemistry is inseparable from Physics , and Biology is inseparable from Chemistry , when analysis conducts us to ultimate principles , yet such distinctions are necessary and convenient .
Physics did not ( according to Comte ) begin definitely to disengage itself from Metaphysics , and to take a truly positive character , until after the great discoveries of Galileo , on the fall of heavy bodies ; whereas Astronomy was really positive , under the purely geometrical point of view , from the foundation of the School of Alexandria . Here , therefore , we ought not only to look for the direct influence of the greatest complication in the phenomena , but also expect to find the scientific condition of Physics much less satisfactory than that of Astronomy , as well under the speculative point of view , in respect of the purity and the co-ordination of its theories , as under the practical point of view , in regard to the extent and exactness of
the predictions that result from it . In truth , the gradual formation of this science during the two last centuries , was owing to the philosophical impulse of the precepts of Bacon , and the conceptions of Des Cartes , which necessarily made its general progress much more rational , by directly establishing the fundamental conditions of the universal positive method . But , however important this great power may have been in accelerating the natural progress of physical philosophy , the long dominion of the primitive metaphysical habits was so absolute , and the positive spirit , which only use could develop , remained so imperfectly characterised , that this science could not in so short a time acquire complete positivism—a state
n 6 t attained by astronomy itself , as respects the mechanical part of it , before the middle of this period . Thus , starting from the point where our philosophical examination has now arrived , we find in the different fundamental sciences remaining for our consideration , more and more profound traces of the metaphysical spirit from which astronomy , of all the branches of natural philosophy , is now completely freed . This antiscientific-influence will not be found limited to details of slight importance . We shall find that it notably alters the fundamental conceptions of science , which , as it appears to me , has not , even in the case of physics , yet taken entirely its definite philosophical character .
And first , as to the extent of the domain of the science of Physics . Like Chemistry , it has for its object the discovery of the general laws of the Inorganic world . The study of these laws is completely distinct from that of the Science of Life , as from that of Astronomy , which is confined to the consideration of the forms and movements of the great bodies of nature . But the distinction ( a real and indispensable one ) between Physics and Chemistry is less precisely marked , and modern discoveries are rendering it more difficult to be made . There are , however , three general considerations which , taken together , make the division between the two sciences quite distinct .
The first consists in the characteristic connexion between the necessary generality of truly physical questions , and the speciality no less inherent in investigations purely chemical . Even the philosophers of the seventeenth century had some glimpse of this . All the conceptions of physics , properly so called , are more or less applicable to all bodies whatever ; while , on the contrary , every chemical idea necessarily relates to an action peculiar to certain substances , whatever resemblances we may otherwise find between the different cases . This fundamental contrariety between the two
categories of phenomena , is always distinctly marked . Weight , for example , is shown in all bodies j so also are the phenomena of thermology , acoustics , optics , and even of electricity ; there being only a simple inequality of degree in their manifestation . The compositions and decompositions of chemistry , on the other hand , show radically specific properties , varying both in the elementary and compound substances . The apparent exception to the generality of physical studies , in the case of magnetism , was dispelled by the discovery that its phenomena arc only a modification of the undeniably general phenomena of electricity .
The second elementary consideration distinguishing Physics from Chemistry , is of less importance , and indeed it rests on less firm grounds ) than the preceding one , although susceptible of being turned to proper use . It consists in this , that the phenomena considered in physics refer to the masses , and in chemistry to the molecules ; whence the habitual denomination of molecular physics , formerly given to the latter science . But purely physical phenomena arc often molecular . The weight of a mass , for example , is the total weight of all the separate molecules in it .
Again , in chemistry , a certain mass is required to show chemical actipn . Still there is much truth in the distinction . In order to produce chemical phenomena , one , at least , of the bodies between which the chemical action is to take place , must be in a state of extreme division , and even , most frequently , in a state of true fluidity j and without this , the action will not be produced : while , on the contrary , this preliminary condition is never indispensable to , the production of any physical phenomenon , properly so called , but is evenor circumstance always unfavourable to it , although it is not sufficient constantly to prevent it .
Finally , a third general remark is perhaps more suited than any other precisely to distinguish physical plienbmeha fVbm chemiciil . In the forme the constitution of fe their particles may change , although iripst ; frequently ho essential alternation of it actually takes place ; but their nature , that is to say , the composition of their molecules , remains constantly unalterable . In the lattery on th contrary , not only is there always a change of state as respects some one of the bodies in question , but the mutual action of these" bodies necessarily alters their nature :. and it is a modification of this sort that essentially constitutes the phenomenon . The greater number of the agents considered in physics are doubtless susceptible ^ , when their influence is very energetic
or very prolonged , of effecting , by themselves , some compositions and decompositions perfectly identical with chemical action , properly so called and this is why there is so natural and so direct a connexion between Physics and Chemistry . But at this degree of action , the phenomena pass in fact , from the domain of the first science , amd enter that of the second / It appears to me that the ensemble of the preceding considerations suffices to give us a precise definition of the proper object of physics , when strictly circumscribed within its natural limits . We see that in this , science we study the laws which govern the general properties of bodies ordinarily
viewed in their mass , and constantly placed in circumstances capable of maintaining intact the composition of their molecules , and even most frequently their state of aggregation . Besides , to act up to the true spirit of philosophy , we always require that every science worth y of the name have for its evident aim , the establishing , on sure grounds , of a corresponding order of predictions . In order , therefore , to complete the definition , it is indispensable that we add , that the ultimate object of the theories of physics is to foresee , as exactly as possible , all the phenomena which may be presented by a body placed in any given circumstances , excluding always those which could alter its nature . It is not to be doubted that this end
is rarely attained in a complete and perfectly precise manner , but this is only because the science is imperfect . Were its actual imperfection much greater than it is , such would still be its necessary destination . From this simple and summary exposition of the general object of physical investigations , it is easy to perceive that they necessaril y present greater complexity than astronomical studies . The latter are limited to the two most simple and elementary aspects of the bodies there considered , —^ namel y > their forms and / their movements . In Physics , on the contrary , the bodies are accessible to all our senses , —the general conditions which
characterize their actual existence are considered , and they are studied under a great number of different and mutually complicated relations . Physics must inevitably be less perfect than astronomy j and were it not for the extension of the means of exploration in the former , in accordance with the law mentioned in a previous article ,- —the increased imperfection of Physics might be conceived , a priori , as rendering a science impossible . The method o ? Comparison is not more applicable here than in Astronomy ;
but it is otherwise with Experiment . Observation ( no longer confined to that of a single sense ) , and experiment have their most complete development in physics . In organic physics , as will afterwards be seen , it is impossible to obtain the requisite conditions of a perfect experiment . The freedom of choice of the case ( whether natural or artificial ) most fitted to manifest the phenomena best , constitutes the chief characteristic of the art of philosophical experiment , and this freedom is found more in Physics than in Chemistry . It is to the development of the former that the
creation of the art is due . Next to the rational use of the Experimental Method , the application , more or less complete , of Mathematical Analysis forms the principal basis on which the perfection of Physics rests . It is here that the Actual range of this Analysis in natural philosophy finds its limit ; and in the sequel ot Comte ' s work it is shown how chimerical it would be to hope that its domain will be further extended , even to Chemistry , with any real efficacy . The comparative fixity and simplicity of physical phenomena ought naturally to permit an extensive employment of Mathematics , although tf is much less adapted to physical than to astronomical studies . This application may occur under two very different forms , the one direct , the other
indirect . The first takes place when the phenomena are such as to permit of our immediately finding in them a fundamental numerical law , which becomes the basis of a more or less prolonged series of analytical deductions , as in the eminent example of the great Fourier when he created lus beautiful mathematical theory of the distribution of caloric , founded altogether on the principle of the thermological action between two bodies being proportional to the difference pf their temperatures . Most frequently * on the contrary , mathematical analysis is introduced only indirectly , thati w , after the phenomena have been connected with some geometrical or mechanical law by means of a course of experiment more or less difficult , owl then , it is not to physics , properly speaking , that the analysis is app hety but to geometry or mechanics . Among other examples , we may cite tne theories of reflection or of refraction , as respects geometry , and those °
weight or of part of acoustics , as respects mechanics . , The application of mathematics to physics ought only to take pJnce ,, an with extreme circumspection too , when assurance has been obtained of reality of the physical facts from which the mathematical deductions to be made . The neglect of this rule has occasioned numerous analyti labours founded on extreme hypotheses or on chimerical conceptions , •» has often converted physical studies into mere mathematical exercises .
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Citation
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Leader (1850-1860), May 29, 1852, page 520, in the Nineteenth-Century Serials Edition (2008; 2018) ncse2.kdl.kcl.ac.uk/periodicals/l/issues/vm2-ncseproduct1937/page/20/
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