At Maecenas' Reception Room, Stefan Bakałowicz, 1890

He who puts off the hour to begin living rightly;
Is like the yokel who stands at the stream with a sigh:
'I can't get across. I'll wait here till it runs dry.'
Meanwhile, it flows, forever flows on and rolls by.

Horace's Epistles are collections (two of them, but almost always published together) of letters addressed to various people and composed in hexameter verse. They are full of useful moral maxims, but this is poetry, not carefully argued philosophy with a definite point of view. Nonetheless, the mature Horace of the Epistles is definitely reaching out beyond beauty, to get a hold on truth and goodness as well:

So now I lay aside my verses and all other toys. What is right and seemly is my study and pursuit, and to that am I wholly given.