Similarly, there is a category whose objects are groups and whose arrows are the homomorphisms from one group to another.

{quote-book|en|1579|Laurence Thomson|A wee note on Calvin's (wordy) sermons|passage= Oure affections boyle within vs, & wallop, frothing as a seething potte.}}

Aristotle's own doctrine is far from clear. It was this lack of clarity that made possible the medieval controversy between nominalists and realists.

[John] Evelyn was astonished at the immense number of pictures he saw in the Dutch fairs. He attributes the briskness of the trade in paintings to the necessary limitations of the country. The farmer or the citizen of sea-locked Holland, unable to lay out his gains on tracts of land, found a medium for speculation or investment in these works of art.