Hume really knew of any valid reply to Philo's arguments in
the following passages of the _Dialogues_, he has dealt unfairly by the
leader in concealing it:--

"But because I know you are not much swayed by names and
authorities, I shall endeavour to show you, a little more
distinctly, the inconveniences of that Anthropomorphism, which you
have embraced; and shall prove, that there is no ground to suppose
a plan of the world to be formed in the Divine mind, consisting of
distinct ideas, differently arranged, in the same manner as an
architect forms in his head the plan of a house which he intends to
execute.

"It is not easy, I own, to see what is gained by this supposition,
whether we judge the matter by _Reason_ or by _Experience_. We are
still obliged to mount higher, in order to find the cause of this
cause, which you had assigned as satisfactory and conclusive.

"If _Reason_ (I mean abstract reason, derived from inquiries _a
priori_) be not alike mute with regard to all questions concerning
cause and effect, this sentence at least it will venture to
pronounce: That a mental world, or universe of ideas, requires a
cause as much as does a material world, or universe of objects;
and, if similar in its arrangement, must require a similar cause.
For what is there in this subject, which should occasion a
different conclusion or inference? In an abstract view, they are
entirely alike; and no difficulty attends the one supposition,
which is not common to both of them.

"Again, when we will needs force _Experience_ to pronounce some
sentence, even on those subjects which lie beyond her sphere,
neither can she perceive any material difference in this
particular, between these two kinds of worlds; but finds them to be
governed by similar principles, and to depend upon an equal variety
of causes in their operations. We have specimens in miniature of
both of them. Our own mind resembles the one; a vegetable or animal
body the other. Let experience, therefore, judge from these
samples. Nothing seems more delicate, with regard to its causes,
than thought: and as these causes never operate in two persons
after the same manner, so we never find two persons who think
exactly alike. Nor indeed does the same person think exactly alike
at any two different per