The purpose of this section of the dissertation is to assess the minimum level of certitude for the thesis proposed, with
an additional comment of any suspected higher level of certitude. There are various levels of certitude that can be chosen.
Opinion is defined as intellectual assent (or disagreement) given to one part of a contradiction with fear of the opposite.70
Possibility is defined as the capacity for existence for a concrete possible thing: internally, that its constituent characteristics
are not impossible, and additionally externally possible, if there is power to produce the thing.71 Probability,
also called likelihood, is defined as the weight of motives, or the accumulation of serious motives, for prudent assent to
some proposition, which is intrinsic probability if the motive arises from the nature of the thing, and can be extrinsic probability
if the motive is from authority, which can also suppose the internal motive.72 Summary of Probabilities is defined
as an accumulation of probable arguments, considered according to their force, which results from a mere juxtaposition. Convergence
of Probabilities is defined as an accumulation of probabilities which converge to produce a sufficient reason. Moral certitude
is defined as firm assent to one part of a contradiction whose necessity arises from the moral law in the physical (not ethical)
sense, e.g., every mother instinctively loves. Physical certitude is defined as firm assent to one part of a contradiction
whose necessity arises from the very physical nature of the thing, e.g., the law of gravity. Metaphysical certitude is defined
as firm assent to one part of a contradiction whose necessity arises from metaphysical necessity, e.g., my own existence.73
Certitude could arise from some observable fact or experiment. However, there is no experiment to prove evolution.74
However, some restricted observation of evolution is possible within species.75
Certitude could arise from some philosophical explanation that exists. Explanations were given by several Neo-Scholastics:
Klubertanz, Renard, Hoenen, Dougherty, Dezza, and O’Flynn Brennan.
Certitude could arise if the argumentation was based on some philosophical principles. The arguments given for Evolutionism
as philosophically possible were based on the principle of causality and the principle of sufficient reason.
Certitude could arise if the explanation is sufficient, due to the principle of sufficient reason. Klubertanz’s explanation
of the possibility of Evolutionism was given in depth, and appeared to be reasonable sufficient.
Certitude could arise if the explanation was rooted in St. Thomas Aquinas, thereby being faithful to tradition. Klubertanz’s
explanation of evolution in this dissertation was paralleled with citations from Aquinas.
Certitude could arise if Neo-Scholastics agree on the possibility of Evolutionism. Some fully agree, such as Klubertanz,
Renard, Hoenen, Dougherty, Dezza, and O’Flynn Brennan. Others partially agree, such as Boyer, who holds evolution only
within species, and La Vecchia who holds evolution between species and genus.76
Certitude could arise due to recent scientific confirmation. Nogar considered all the convergent scientific arguments and
argued in favor of evolution without restriction.77 The Darwin Centennial Celebration at the University of Chicago
in 1959, attended by 50 outstanding international experts, had excellent agreement among scientists on the fact of evolution.78
At the Gregorian University in Rome, La Vecchia considered the arguments favoring evolution from biology and arguments opposed;
and La Vecchia considered the arguments favoring evolution from paleontology, and arguments opposed; it was then that La Vecchia
concluded to limited evolution. The International Congress on Evolution, in Rome from 23 to 24 April 2002, presumed that evolution
was the "crossroad" of science, philosophy and theology for "a lively dialogue between specialists of varied disciplines..."79
Certitude could arise if the opposite opinion is not tenable. Norgar states, "Creationism is an unsatisfactory solution
to the manifold data in the in the dynamic sciences, as well as the static biological sciences, in neo-biology as well as
paleobiology."80
Certitude could arise if the objections of adversaries are able to be answered.
FIRST OBJECTION: Like produces like ("Oportet agens esse simile facto," Aquinas Summa Theologiae 1. 91. 2; and "Simile
fit a suo simile," Aquinas Summa Theologiae 1. 65. 4), so no substantial change is to be expected. Aristotle teaches
the action of individual natural causes is necessary, predetermined. Here are treated causes that do not have free will. The
acorn from an oak tree will grow into another oak.81 REPLY: Although individual lines of causality in the world
are necessary, there is no necessity about their crossing or interference.82 At the level of the created causes
involved in evolution this interference is uncaused, and so contingent. Chance interference of two lines of causality can
usually be expected to spoil the effect produced, which would be regressive evolution. But it is theoretically conceivable
that the chance effect, equivalent causality, would be proportionate to a higher nature.
SECOND OBJECTION: All nature is ordered to produce its proper perfection and not for its destruction. But to become another
species would be to destroy the first perfection (first species). Therefore, nature does not tend to change to another species,
namely for its first species to cease.83 REPLY: Nature can also be defined as the whole system of inter-related
natures. Although the natural potency in a thing implies an intrinsic order to an act, giving rise to a relation between an
appetite and the good, this good need not be considered as a perfection of the thing in its own particular being. In fact,
in the case of non-living things, it is very difficult to determine just what is the good for them. But it is different if
the general scheme of the universe is considered. Then the observed tendencies very often appear as contributing to the order
and good of the whole, seen in the framework of the general intention of universal nature.84 Further, St. Thomas
notes that the existence of nature is clearly known by itself, since natural things are manifest to the senses, but it is
not manifest what the nature of any thing actually is, nor is its principle of motion manifest.85
Certitude can be had from the possibility of philosophers and theologians admitting this mode of origin without damage
to their other beliefs. Reasonable arguments have been given to philosophers.86 Belief in the Bible is not damaged
for theologians.87
Certitude can be had from the fact that evolutionism is the best answer now for the origin of the species.88
St. Thomas makes a distinction between a "verified" universal (dici de omni) and a "provisional" universal (ut nunc).89
This provisional universal, within a working hypothesis, is very useful in the investigation of nature. An example of a verified
universal (dici de omni) is that in a right triangle every right angle has ninety degrees. An example of a provisional
universal (ut nunc) is "white" predicated as a common property of swans, or evolution predicated as the common property
of every origin of species. The example of the right triangle is a property based on certain (propter quid) demonstration.
The example of the white swans is based on an incomplete (quo) induction, since the reporters had never seen a black
swan. Thus, evolution predicated as the common property of every origin of species is the best answer we have now.90
The level of certitude for "Evolutionism is philosophically possible" is at minimum at the level of the possible. The proof
is the convergence of all of the above arguments, especially the fulfillment of the principle of sufficient reason. This agrees
with the opinion of Klubertanz.91 However, there is the suspicion that the thesis could be at the level of the
probable. Maritain seems to be "convinced" that Evolutionism is compatible with the views of St. Thomas, and Bittle agrees
the theory can be "probable."92 Nogar would assess the thesis are "more probable."93 Therefore, we can
conclude that the thesis as described and defended is at least possible, and perhaps even a "convergence of probabilities."94
Having come to the correct conclusion on the philosophical level of certitude, the philosopher must still conclude with
some humility. The philosophy of nature does not disregard the objects observed and perceived by sense.95 This
is the method of Aristotle and St. Thomas.96 This method is confirmed by the Neo-Scholastic Jacques Maritain: "It
is the upward resolution toward intelligible (as compared with the sensible) being... In this process the sensible object
is not lost sight of..."97 Yet Klubertanz rightly reminds the philosopher, "On the other hand, the factual occurrence
of such evolution in the case of particular organisms, which actually existed in a given time in world history, is a question
of fact whose establishment by any direct means is extremely difficult if not impossible."98 Thus, scientific fact,
in general or regarding evolution, does touch philosophy of nature. Gardeil notes, "The respective limits of philosophical
and scientific investigation are not so easy to determine as might at first appear...The philosopher of nature cannot altogether
ignore...science."99 Why can’t Evolutionism be declared philosophically certain? The responsible philosopher
cannot ignore the lingering doubt about the scientific fact of evolution.
