Devoir de Philosophie

Chemistry, philosophical aspects of

Publié le 22/02/2012

Extrait du document

Chemistry, like all theoretical sciences, is deeply rooted in philosophical inquiry. Early Greek atomism was a response to Parmenides' argument that the very concept of change is unintelligible. Aristotle in turn argued that a vacuum is impossible and proposed that qualitative change could be better understood in terms of four elements and an underlying prime matter. During the Arabic and Latin Middle Ages, philosophical commentaries on the nature of materials were brought into juxtaposition with the practical arts of the alchemist, miner and pharmacist. As chemical speculations became more closely connected to observations during the time of the Scientific Revolution, natural philosophers became more and more interested in the methodological aspects of chemistry. Galileo and Locke tried to clarify the relationship between primary and secondary qualities. Boyle struggled to understand how the selective affinities so characteristic of chemical reagents could be explained within the framework of Descartes' mechanical philosophy. Lavoisier's textbook was organized around principles drawn from philosophes such as Condillac. As chemistry became an autonomous science, chemists turned less often to philosophy as a source of theoretical inspiration. However, they frequently appealed to philosophies of science in order to defend their own theories or criticize those of their opponents. The so-called 'atomic debates' amongst chemists in the British Association during the 1860s were primarily disputes about the epistemological legitimacy of appeals to unobservable entities. Many of the same issues were taken up at the end of the century by Ostwald, Mach and Duhem.

« only in size or shape.

The processes we observe around us are the result of changing groupings or arrangements of atoms; the qualitative aspects of experience are the results of their collisions with the atoms of our soul or mind. However, Democritus is very explicit that we cannot expect to have knowledge of qualities. By convention are sweet and bitter, hot and cold, by convention is colour; in truth are atoms and the void. …There are two forms of knowledge, one genuine, one obscure.

To the obscure belong all of the following: sight, hearing, smell, taste, touch. (Kirk and Raven 1962: 422) The atomistic tradition was continued by Plato who, in the Timaeus , gave an elaborate geometrical account of atoms in terms of the five regular polyhedra ( Plato §16 ).

In The Nature of Things , Lucretius provided speculative corpuscular explanations of everything from evaporation to sexual attraction, but in part because of its historical connections to Epicurean moral philosophy, atomistic theorizing became theologically suspect and was not further developed until the rise of modern science ( Epicureanism §§3, 12 ). The dominant theory of matter was Aristotle 's sophisticated account of the four elements - earth, air, fire and water (an account earlier developed by Empedocles).

Aristotle posited an underlying substratum of prime matter that could neither be created nor destroyed.

On it were impressed various combinations of the four fundamental qualities, the hot or the cold, the wet or the dry.

The four elements could be transmuted into each other.

For example, by adding more warmth to water (formed from the cold and the wet) one could change it into air (characterized as the hot and the wet) ( Matter §1 ). In trying to explain the multiplicity of properties which we actually observe, Aristotle associated additional qualities with each element.

Thus softness and ductility and a bland taste are characteristic of water.

Brittle materials are earthy, while sour or spicy foods contain fire.

Not only do ordinary materials contain varying proportions of the elements, they also differ in how intimately the parts are combined. Although there are places where Aristotle seems to presuppose a sort of conservation law for his qualities, there are also passages in which he says that the more potent properties can completely transform the weaker.

Thus if a great quantity of water is added to wine, in the end the water will actually convert the wine into water.

In a similar way, Aristotle says, living things can transform food into flesh and bone ( De generatione et corruptione I 5).

The Aristotelian system thus provided the philosophical foundation for alchemy ( Alchemy ). 2 Corpuscles, forces and conservation Greek atomism had postulated that all processes could be understood as the result of collisions between, and regroupings of, invisible particles, but it had very little to say about how or why the atoms moved or what caused them to cohere into relatively stable clusters.

Both of these deficiencies were addressed by the theories of motion developed in the seventeenth century.

Although Descartes rejected the possibility of a vacuum, his programme of. »

↓↓↓ APERÇU DU DOCUMENT ↓↓↓

Liens utiles