Most people treat tiredness as a signal to stop. But the 11th-century Persian philosopher Avicenna noticed something subtler in his medical canon: the body and mind don't fatigue uniformly — different capacities deplete at different rates, and what feels like global exhaustion is often one specific faculty hitting its limit while others remain intact. This maps onto something modern exercise scientists call 'differential fatigue,' but Avicenna's version goes deeper: he argued that the rational soul and the animal soul (his term for our instinctive, physical drive) exhaust themselves through different activities and replenish through different means. The person who feels 'too tired to lead' after a hard workout may have depleted their physical faculty while their deliberative capacity remains largely untouched — or vice versa. Knowing which specific faculty is spent, rather than assuming you're simply done, lets you route your remaining energy more honestly.

What would remain of your capacity today if you stripped away the assumption that tiredness in one area means tiredness across all areas?

Drawing from Islamic Neoplatonism / Avicennan Psychology — Ibn Sina (Avicenna, The Canon of Medicine / Al-Qanun fi al-Tibb, c. 1025 CE)