670 PSYCHOLOGY. 



etc., etc. Such principles as these, which might be multi- 

 plied to satiety,* are properly to be called postulates of 

 rationality, not propositions of fact. If nature did obey 

 them, she would be pro tanfo more intelligible ; and we seek 

 meanwhile so to conceive her phenomena as to sIioav that 

 she does obey them. To a certain extent we succeed. For 

 example, instead of the 'quantity of existence' so vaguely 

 postulated as unchanged, Nature allows us to suppose that 

 curious sum of distances and velocities which for want of 

 a better term we call 'energy.' For the eflect being 'con- 

 tained in the cause,' nature lets us substitute ' the effect is 

 the cause,' so soon as she lets us conceive both effect and 

 cause as the same molecules, in two successive positions. — 

 But all around these incipient successes (as all around the 

 molecular world, so soon as we add to it as its ' effects ' those 

 illusory ' things ' of common-sense which we had to butcher 

 for its sake), there still spreads a vast field of irrationalized 

 fact whose items simply are together, and from one to 

 another of which we can pass by no ideally ' rational ' way. 

 It is not that these more metaphysical postulates of 

 rationality^ are absolutely barren — though barren enough 

 they were when used, as the scholastics used them, as 

 immediate propositions of fact.f They have a fertility as 



* Perhaps the most influential of all these postulates is that the nature 

 of the world must be such that sweeping statements may be made about it. 



f Consider, e.g., the use of the axioms ' neino potest supra seipsum,' and 

 'nemo dat quod non habet,' in this refutation of 'Darwinism,' which I take 

 from the much-used scholastic compendium of Logic and Metaphysics of 

 Liberatore, 3d ed. (Rome, 1880): " Ha?c hypothesis . . . aperte coutra- 

 dicit priucipiis Metaphysicse, quae docent essentias rerum esse immuta- 

 biles, et effectum non posse superare causam. Et sane, quando, juxta 

 Darwin, species inferior se evolvit in superiorem, imde trahit maiorem illam 

 nobilitatem? Ex ejus careutia. At nihil dat quod non habet ; et minus 

 gignere nequit plus, aut negatio positionem. Prgeterea in transformatione 

 quae fingitur, natura prioris speciei, servatur aut destruitur? Si primum, 

 mutatio erit tantum accidentalis, qualem reapse videmus in diversis stirpi- 

 bus animantium. Siu alterum asseritur, ut reapse fert hypothesis darwin- 

 iana, res tenderet ad seipsam destruendam ; cum contra omnia naturaliter 

 tendant ad sui conservatiouem, et nonuisi per actionem contrarii ageutis 

 corruant." It is merely a question of fact w^hether these ideally proper 

 relations do or do not obtain between animal and vegetable ancestors and 

 descendants. If they do not, what happens? simply this, that we cannot 

 continue to class animal and vegetal facts under the kinds between which 



