s, which maketh as well the feathers in birds as the hair in
beasts, passeth in birds through a finer and more delicate strainer
than it doth in beasts. For feathers pass through quills, and hair
through skin." It is an instance of percolation or filtering: other
effects of the same cause being the gums of trees, which are but a
fine passage or straining of the juice through the wood and bark,
and Cornish Diamonds and Rock Rubies, which are in like manner "fine
exudations of stone".[4]

These examples of Bacon's Inductions are taken from the _Sylva_ at
random. But the example which best of all illustrates his attitude
as a scientific investigator is the remark he makes in the _Novum
Organum_ about the Copernican theory. Elsewhere he says that there
is nothing to choose between it and the Ptolemaic; and in the _Novum
Organum_ (lib. ii. 5) he remarks that "no one can hope to terminate
the question whether in diurnal motion it is really the earth or the
sky that rotates, unless he shall first have comprehended the nature
of spontaneous rotation". That is, we must first find out the
_forma_ or formal cause of spontaneous rotation. This is a veritable
_instantia crucis_, as fixing Bacon's place in the mediaeval and not in
the new world of scientific speculation.

Bacon, in short, in the practice of induction did not advance an inch
beyond Aristotle. Rather he retrograded, inasmuch as he failed to draw
so clear a line between the respective spheres of Inductive
collection of facts and Explanation. There are two sources of general
propositions, according to Aristotle, Induction and Nous. By Induction
he meant the generalisation of facts open to sense, the summation of
observed particulars, the _inductio per enumerationem simplicem_ of
the schoolmen. By Nous he meant the Reason or Speculative Faculty,
as exercised with trained sagacity by experts. Thus by Induction we
gather that all horned animals ruminate. The explanation of this is
furnished by the Nous, and the explanation that commended itself to
the trained sagacity of his time was that Nature having but a limited
amount of hard material and having spent this on the horns, had none
left for teeth, and so provided four stomachs by way of compensation.
Bacon's guesses at causes are on the same scientific level with this,
only he rather confused matters by speaking of them as if they were
inductions from fact, instead of being merely fancies superinduced
upon fact. His the