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it is day, it is light'. This is true; for 'it is not light', being the opposite
of the conclusion, conflicts with 'it is day'. A conditional is false if the
opposite of the conclusion does not conflict with the antecedent, for
example, 'if it is day, Dion is walking'; for 'it is not the case that Dion
is walking' does not conflict with 'it is day'.
- A paraconditional is true if it begins with a true [proposition] and
concludes with one which follows [from it], for example, 'since it is day,
the sun is over the earth.' A false [paraconditional] is one which either
starts with a false [proposition] or concludes in one which does not follow
from it, for example, 'since it is night, Dion is walking', if it is said when
it is day. A true causal [proposition] is one which begins from a true
[proposition] and concludes in one which follows from it, but whose first
[proposition] does not follow from the conclusion; for example, 'because
it is day, it is light'. For 'it is light' follows from 'it is day' and 'it is day'
does not follow from 'it is light'. A false causal [proposition] is one which
either [1] begins from a falsehood or [2] concludes in a [proposition]
which does not follow from it or [3] one whose first [proposition] follows
from the consequent. - A persuasive proposition is one which leads to assent, for example,
'if someone gave birth to something, she is its mother'. But this is false;
for the bird is not the mother of the egg.
Again, some [propositions] are possible and some are impossible; and
some are necessary and some are not necessary. That [proposition] is
possible which admits of being true, if external factors do not prevent
it from being true, for example, 'Diodes is alive'. That [proposition] is
impossible which does not admit of being true, for example, 'the earth
flies'. The necessary is that which, being true, is not receptive of being
false, or is receptive of being false but external factors prevent it from
being false, for example, 'virtue is beneficial'. The non-necessary is that
which both is true and is able to be false, with external factors not
opposing it at all, for example, 'Dion is walking'. - A reasonable proposition is one which has more chances at being
true [than not], such as 'I will be alive tomorrow'.
And there are other differences among propositions and changes of
them from true to false, and conversions; these we discuss in a general
fashion.
As the followers of Krinis say, an argument is what is composed of a
premiss, an additional statement, and a conclusion. For example, some-
thing like this:
If it is day, it is light.
It is day.
Therefore, it is light.