Cock-sure certainty is the source of much that is worst in our present world, and it is something of which the contemplation of history ought to cure… - Bertrand Russell

The past alone is truly real: the present is but a painful, struggling birth into the immutable being of what is no longer. Only the dead exist fully. The lives of the living are fragmentary, doubtful, and subject to change; but the lives of the dead are complete, free from the sway of Time, the all but omnipotent lord of the world. Their failures and successes, their hopes and fears, their joys and pains, have become eternal—our efforts cannot now abate one jot of them. Sorrows long buried in the grave, tragedies of which only a fading memory remains, loves immortalized by Death's hallowing touch these have a power, a magic, an untroubled calm, to which no present can attain. ...On the banks of the river of Time, the sad procession of human generations is marching slowly to the grave; in the quiet country of the Past, the march is ended, the tired wanderers rest, and the weeping is hushed.

I do not pretend to start with precise questions. I do not think you can start with anything precise. You have to achieve such precision as you can, as you go along.

Whatever we know without inference is mental.