Afurtherdifficultyisraisedbythefactthatallknowledgeis
ofuniversalsandofthe’such’，butsubstanceisnotauniversal，but
israthera’this’-aseparablething，sothatifthereisknowledge
aboutthefirstprinciples，thequestionarises，howarewetosuppose
thefirstprincipletobesubstance？