Wallflower, in case you got lost sometime between when you replied to me and now (which I think is very likely) I answered your question on page forty of this thread: http://www.cathinfo.com/catholic.php?a=topic&t=31535&min=195&num=5
I would also like to add (since it's too late) a relevant quote from McHugh and Callan on moral certainty, and it's much too late to edit my reply:
643. Kinds of Certitude.--Judgments may be certain in a greater or less
degree.
(a) They are metaphysically certain, when error is absolutely
impossible, the opposite of what is held by the mind being a
contradiction in terms which omnipotence itself could not make true.
Example: The judgments that the same, identical act cannot be both good
and bad, that good is to be done and evil to be avoided, that God is to
be honored, are metaphysically certain, since they result immediately
from the very concepts of being, of goodness, and of God.
(b) Judgments are physically certain, when error is impossible
according to the laws of nature, the opposite of what is held by the
mind being unrealizable except through intervention of another cause.
Example: The judgments that he who takes poison will destroy life, that
he who applies fire to a house will destroy property, are physically
certain. because natural agencies, like poison and fire, act infallibly
when applied to suitable matters and under suitable conditions and left
to their course, unless they are overruled by superior power.
(c) Judgments are morally certain, when error is impossible according
to what is customary among mankind, the opposite of what is held by the
mind being so unlikely that it would be imprudent to be moved by it.
Examples: One is morally certain that what a reputedly truthful and
competent person relates to one is true. A person is morally certain
that a conclusion he has drawn about his duty in a particular instance
is correct, if he believes that he has overlooked no means of reaching
the truth. Testimony and inference, since they come from free and
fallible agencies, may lead into error; but, when they appear to have
the requisite qualities indicative of truth, they are for the most part
reliable and in practical life have to be considered as such.
...
644. As to the certainty that is required in the judgment of
conscience, the following points must be noted:
(a) Metaphysical certainty is not required, since conscience does not
deal with primary propositions, but with deductions about particular
acts. The first moral principles, which are the object of synderesis,
and at least some of the general conclusions, which are the object of
moral science, are metaphysically certain (see above 145, 300), as they
are based on necessary relations; but the particular conclusions, which
are the object of conscience, are concerned with the contingent and the
individual.
(b) Physical certainty is not required for the judgment of conscience,
since conscience is not concerned with the activities of natural
agents, but with the activities of moral agents that act with freedom
and responsibility.
(c) Moral certitude, therefore, is sufficient for the conclusions drawn
by conscience. That a higher kind of certitude is not necessary should
not surprise us, for it would be unreasonable to expect that the same
degree of assent be given to judgments that are concerned with
particular and contingent cases as to those that are concerned with
universal and necessary principles.
...
646. Moral certitude in the wide sense is sufficient for a safe
conscience, even in matters of great importance, since it is frequently
the only kind of certitude one can have, and he who would strive to be
free from every slight and baseless suspicion would be soon involved in
a maze of scruples and perplexities.
Source: McHugh and Callan
Thank you! I've been procrastinating coming back to this out of dread for the time it would take to pick through and find the post!
I have a little more time today. I'll post this first so I can go back to reread it more easily.