Tahafut_al-Tahafut-transl-Engl-van-den-Bergh

GENUS AND SPECK DIFFERENCE CANNOT BE APPLIED
TO IT,
Ghazali says:
Indeed, they are all of this opinion, and they deduce from
this that, since nothing can share its genus, it cannot be
differentiated through a specific difference and cannot have
a definition, since a definition is constructed out of genus
and specific difference and what has no composition cannot
have a definition, for a definition is a kind of composition. ‘
And they affirm that, since the First is said to resemble the
first effect in being an existent and a substance and a cause
for other things, and to differ from it in other respects, this
certainly does not imply sharing in its genus; no, it is nothing
but a sharing in a common necessary attribute. The
difference between genus and necessary attribute consists
in their content, not in universality, according to logical
theory, for the genus, namely, the essential universal, is the
answer to the question what the thing is, and is subsumed
under the quiddity of the thing defined, and constitutes its
essence: a man’s being alive is subsumed under the quiddity
of man, i. e. his animality, and is his genus, but his being
born and created are his necessary attributes, and, although
they are universals which can never be separated from him,
are not subsumed under his quiddity, according to logical
theory, about which there can be no misgiving. ; And the
philosophers affirm that existence is never subsumed under
the quiddity of things, but stands in a relation to the quiddity,
either necessarily and inseparably, like its relation to heaven,
or subsequently, after their nonexistence, like its relation to
temporary things, and that the sharing of existence does not
imply a sharing in genus. And as to its sharing in ‘being a
cause to other things’ with all the other causes, this is a
necessary relation which likewise cannot be subsumed
under the quiddity, s for neither the fact of being a principle
nor existence constitutes the essence, but they are
necessary attributes of the essence, consequent upon the
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