In his Meditations, Marcus Aurelius prompts us:
You shouldn’t be surprised that a fig tree produces figs.
He goes on to state that “A good doctor isn’t surprised when his patients have fevers, or a helmsman when the wind blows against him.” The truth Marcus is getting at here, or at least as I understand it, is that past performance is a reasonable indicator of future results.
This isn’t always the case, as no doubt that last sentence reminded you of the common “Past performance is no guarantee of future results” line that is, sensibly, plastered across risky investment products. But in life, as with fig trees, medical patients, and the blowing winds upon the shore, past performance is no guarantee of future results… but it’s a reasonable bet. ∎