Notes, ii. i. 151 



It is evident then why A. holds it more accurate to say composition from the elementary 

 forces rather than from the elements, the former being the components of the latter. 

 It is plain also that when he says "nor out of all of them," he means to exclude all 

 other properties excepting the four main ones, two of which belong to every tangible object. 

 From these four primary properties, he says, all others are derived, and in contrast to 

 them may be called" secondary. As to the mode in which .the secondary properties are 

 deducible from the primary ones, cf. D. G. et C. ii. 2. 



It will be noticed that A. uses the adjectival forms, hot, cold, solid, fluid, and not 

 the substantives, heat, fluidity, etc. For he is speaking not of abstract properties, 

 but concrete substances. His views [D. G. et C. ii. i) were as follows. There is one 

 ultimate matter, which forms the universal substratum of all terrestrial things. This 

 matter however has no existence in a condition of isolation, but is invariably combined 

 with some or other of the primary properties, heat, fluidity, etc. Thus we have fluid 

 matter, hot matter, solid matter, cold matter ;. but there is no such thing as simple matter 

 by itself, any more than there is such a thing as fluidity by itself. By hot, cold, solid, 

 fluid, A. means then the universal substratum ' in a state of heat, coldness, solidity, or 

 fluidity. 



Even hot matter, solid matter, etc., are however not forthcoming as actual existing 

 bodies; for matter, as already explained, is always combined with more than one. of 

 the four primary properties.* The simplest producible substances would therefore be 

 those formed by matter in combination with two properties, that is the elementary 

 substances, earth, air, fire, water. But even these are nob actually forthcoming in 

 absolute purity ; for the substances we know as earth, air, water, fire, are not the pure 

 elements themselves, but compounds of all four, in which one element so preponderates 

 as to give its general character and name to the whole. (See next note.) 



It is usual to render \rff6v and i,-r\p6v as wet and dry, and not, as I have rendered them, 

 fluid and solid. But A. can never have supposed wetness to be one of the primary 

 properties of matter. The definitions, moreover, given by him {D.G. et C. ii. 2) are 

 conclusive. " Wet (StepJ*') is that which has extraneous liquid on its surface ; Soaked 

 (ffefipfyixivov) is that which has it in its substance. Fluid (iiyp6i/) is that which has 

 no form of its own, but readily accepts one. Solid (|?7/>(J»') is that which has a distinct 

 form of its own, and resists the imposition of a fresh one. " 



We know, at the present day, that the physical condition of a substance is distinct 

 from its chemical composition ; a substance may be hot or cold, solid, fluid, or gaseous, 

 while all the time its deeper-lying chemical composition remains unchanged. But A. 

 knew of no such distinction. Physical and chemical qualities were to him one and 

 the same thing ; substances differed from each other in their composition, because of 

 the diff"erent proportions in which the fundamental physical properties were intermixed 

 to constitute them. Water, for instance, in its ordinary fluid condition, consisted of 

 cold ma^tter and fluid matter. When such water became vapour, it changed not 

 merely its physical condition but its composition, hot matter being added to the former 

 constituents ; and similarly its composition was altered by another addition when it 

 became ice. 



4. By compound substances A. means all substances made by combinations of the 

 elements. " Some substances are simple, others compounds of these. By simple 

 substances I mean those that have natural motions, such as fire, earth, and the like, 

 and their several fornjs " [De Ccelo, i. 2, 4). In one sense indeed even the elements are 

 compound (see last note) ; but it is of compounds out of the elements that A. is here 

 speaking. Every suph compound, that is every actually existing substance, contains, says 



