Irrealis “were” following “as if”
Is the subjunctive “were” in the sentence, “He seems as if he were spell-bound,” construed as counterfactual? Does it always preclude truth, or does it only here suggest that it was highly improbable that the subject, “he,” was spell-bound?
If I exchanged a past-conditional “was” for the “were” would it open possibilities in the sentence? And would a present indicative “is” make any sense at all? The present tense doesn’t seem to me well fitted to the phrase “as if.”
And if I could ask a question further: when were these distinctions drawn between “were,” “was,” and “is” regarding the phrase “as if”?
Thank you for your time!
“He seems as if he were spell-bound,” construed as counterfactual?
It seems to be the case - this is not the same as "it is the case".
"as if he were" approximates to "that he might be"
The speaker is expressing a possible description/explanation by comparing the subject's condition to a recognisable condition.
Does it always preclude truth,
No. The speaker's guess could be correct.
or does it only here suggest that it was highly improbable that the subject, “he,” was spell-bound?
This would depend upon the context. (It is difficult to express how important context is in English) (i) It may be probable if the subject were the prisoner of a wizard, then it is quite possible that he is spellbound - although the subjunctive and "seems" allow for other possibilities. (ii) If the subject were a modern businessman, as there is no such thing as magic, then the subject is not "spellbound" other than, perhaps in a figurative sense.
TO ADD
when were these distinctions drawn between “were,” “was,” and “is” regarding the phrase “as if”?
Old English had the subjunctive.