P61: A Desire that arises from reason cannot be excessive.

Dem.: Desire, considered absolutely, is the very essence of man (by Def. Aff. I), insofar as it is conceived to be determined in any way to doing something. And so a Desire that arises from reason, i.e. (by IIIP3), that is generated in us insofar as we act is the very essence, or nature, of man, insofar as it is conceived to be determined to doing those things that are conceived adequately through man’s essence alone (by IIID2). So if this desire could be excessive, then human nature, considered in itself alone, could exceed itself, or could do more than it can. This is a manifest contradiction. Therefore, this Desire cannot be excessive, q.e.d.