推測 and 推察: Clues to size, actions, and fatigue
Compare inferences from footprint shape, footprint direction, and expression. Read the clue and inferred content while preserving limited knowledge, possibility, and each example's stated participants.
Estimating an animal's size from shape
推測 includes inference or estimation. The footprint-shape example states both the available clue and the animal's size estimated from it.
「足跡の形から動物の大きさを推測した。」 (I estimated the animal's size from the shape of its footprints.) The clue is the shape of footprints, and the inferred content is size. This does not report measuring the animal directly or obtaining a confirmed numerical size.
Inferring an action or fatigue from a clue
推察 also includes inference or conjecture. The example about footprint direction concerns an action, so the word is not confined to reading emotions or thoughts.
「詳しい事情は分からないが、表情から疲れていると推察できる。」 (I do not know the details, but his expression suggests that he is tired.) The Japanese leaves the person's gender unspecified; “his” belongs to this English translation. The detailed circumstances are unknown, but the Japanese says fatigue can be inferred from expression; this is not a confirmed diagnosis.
Separate the clue from what is inferred
「足跡の向きから、彼が山へ入ったと推察した。」 (From the direction of the footprints, I inferred that he had entered the mountains.) The route into the mountains is inferred from footprint direction. This does not become direct observation of the person entering the mountains.
Do not divide the terms into object-only and person-only uses. Compare shape, direction, or expression with the inferred size, action, or fatigue, keeping the separate examples from becoming one footprint event or one person's chronology.
How do estimating animal size with 推測 from footprint shape and inferring entry into the mountains with 推察 from footprint direction compare?
Show the answer and why
The first infers size from shape; the second infers an action from direction. Both derive content from clues without establishing direct measurement or observation. The action example also prevents restricting 推察 to a person's emotions.