the philosopher is the friend and welcomer of differences, the insister on their value and seriousness. But as before, he will not accept as real and genuine all differences, nor all at the same value. Some he will roundly denounce as spurious. To deserve and win his recognition a difference must vindicate its claim, must legitimate itself by disclosing its basis and its implication with the unity which together with it forms its terms into a system. Trivial, insignificant arbitrary differences imply and are implied by trivial, insignificant arbitrary unifications. Where system is not exhibited, difference and unity are alike unsound—neither can be called genuine or real. And in particular the differences drawn and used by practical common sense, or even by the sciences, deserve just as much, and just as little, respect as the hurriedly formed aggregations and collocations, proudly termed 'classes' and 'laws', with which they are inseparably connected.
All this applies to the crude though sometimes elaborate, attempts made to enumerate and classify kinds of difference, or to arrange them in a scale or hierarchy. Not that the aim and design of these attempts is erroneous: it is the execution that is at fault. Nothing could be more foolish in the philosopher than a prejudice against recognizing differences of differences, but these too he cannot take as they are offered to him, or at the current value which they bear in ordinary life or in scientific treatises. That they 'work' there is indeed significant to him and sets him a problem, but it does not guarantee the value assumed for or ascribed to them. He must assay them by his own tests, and so tried some of them prove base metal enough, mere tokens and counters in the hazardous operations of the common mart where the ordinary
