We must consider next the work of distinction in itself. First, the work of the first day; secondly, the work of the second day; thirdly the work of the third day.

Under the first head there are four points of inquiry:

A1 Whether the word light is used in its proper sense in speaking of spiritual things?

A2 Whether light, in corporeal things, is itself corporeal?

A3 Whether light is a quality?

A4 Whether light was fittingly made on the first day?