But is it in fact found that _undisputed_ points are always such as
have been the most carefully examined as to the evidence on which they
rest? that facts or principles which are taken for granted, without
controversy, as the common basis of opposite opinions, are always
themselves established on sufficient grounds? On the contrary, is not
any such fundamental point, from the very circumstance of its being
taken for granted at once, and the attention drawn off to some other
question, likely to be admitted on insufficient evidence, and the
flaws in that evidence overlooked?

Experience will teach us that such instances often occur: witness the
well-known anecdote of the Royal Society; to whom King Charles II.
proposed as a question, whence it is that a vessel of water receives
no addition of weight from a live fish being put into it, though it
does, if the fish be dead. Various solutions, of great ingenuity, were
proposed, discussed, objected to, and defended; nor was it till they
had been long bewildered in the inquiry, that it occurred to them _to
try the experiment_; by which they at once ascertained that the
phenomenon which they were striving to account for,—which was the
acknowledged basis and substratum, as it were, of their debates,—had
no existence but in the invention of the witty monarch.[3]

Another instance of the same kind is so very remarkable that I cannot
forbear mentioning it. It was objected to the system of Copernicus
when first brought forward, that if the earth turned on its axis, as
he represented, a stone dropped from the summit of a tower would not
fall at the foot of it, but at a great distance to the west; _in the
same manner as a stone dropped from the mast-head of a ship in full
sail, does not fall at the foot of the mast, but towards the stern_.
To this it was answered, that a stone being a _part_ of the earth