In Plato and Aristotle ancient speculation reached its culminating point, and to us at the present day they appear to stand far above all who followed them, and yet it is very noteworthy how slight was the in?uence they exercised over the thinkers of the three following centuries. Their systems were neither accepted as final, and as rendering unnecessary any further inquiry, except in the way of comment and illustration; nor, on the other hand, were they sharply criticized; their shortcomings pointed out, and new theories formed with the endeavour at least to avoid their supposed errors. They were neither used as models nor warnings. The very faults they are most.