Our reason for considering the meaning of equivocal terms is that the term "evolution" is used about many things with many different meanings among themselves. There is perfect unity in vocabulary, the word "evolution." But there is no unity in concepts, sometimes biological, anthropological, cosmological, sociological, or irreligious.⁶ It is useful to point out that the "proofs" about biological evolution do not immediately transfer to applications of the word "evolution" to other fields, where the meaning of the term evolution differs even as the field itself is different. Nogar is careful to begin his book, The Wisdom of Evolution, by stating, "This book marks off the limits of evolution by logical analysis, manifesting what generalizations flow from the scientific facts and what generalizations do not."⁷

Univocal term is one that is predicated of many things according to the same signification entirely. For example, "man" is predicated of Peter, Paul and John.

Equivocal term is one that is predicated of many things according to an entirely diverse signification.⁸ For example, "dog" is predicated about a four-legged animal, or the dogfish, or the dog star. Equivocal terms can be predicated by chance or by design. Equivocal by chance is a predication without any reason. Equivocal by design can be without a foundation in the thing itself, or with a foundation in the thing itself. An example of equivocal by design without foundation in the thing itself would be naming a child John with the hope that the child would imitate the virtues of St. John. An example of equivocal by design with foundation in the thing itself (also called "analogy") is the predication of the term "healthy" of a person, of food, of medicine, or of healthy face color.

Analogical term is one that is predicated by design with a foundation in the thing. Analogy of proportion (or attribution) is predicated by order, the first thing primarily and the rest secondarily, so health is predicated first about man, and then all the things that lead to human health such as medicine. Analogy of proportionality (or proportion) arises from mathematics (the proportionality of 10:5 as 8:4), but in analogy of proportionality what is applicable to one is different in the other, such as the foot of a man and the foot of a column.

The general meaning of the term "evolution" is tied to biological transformation of species by mutation and natural selection. Philosophical Evolutionism may attempt to extend that meaning.⁹ Herbert Spencer and some others wish to extend the term "evolution" to the level of a universal law that pertains to all transformation in the universe. Those followers of Darwin, notably Huxley and Spencer in England and Hackel in Germany, made unwarranted extensions of the theory into fields of philosophy and ethics. So evolution, only a modest scientific theory, itself became a philosophy, almost a creed.¹⁰

Evolution in popular usage can mean simply "change." There are many writers that argue if a person admits change, then that person is actually admitting the scientific theory of evolution. Such an argument is "loose thinking."¹¹

The Neo-Scholastic Raymond Nogar promotes the use of the term as a fruitful principle to understand natural science beyond biology. However, Nogar notes that there is no universal "Law of Evolution."¹²

Evolution means biological change or biological development.²⁸

The soul of man has several causes. The soul is a subsistent form. The material cause of the human soul is not "from which", but "in which", it is created, namely, the human body. The efficient cause of the human soul is God, its creator. The final cause is the most important for our purposes here, for it relates to the future of man. The will of man is the appetite of man as a whole, as a rational being; and the object of the of the will is ultimately the supreme good and its possession, which is happiness.²⁹

The soul of man is essentially and personally united to the body as its substantial form.³⁰ The essential unity makes the species complete, so that man is a rational animal. The union is personal because all actions are attributed to the same person. Proof of the unity is from the unity of operation (operatio sequitur esse). Proof of the essential unity is the mutual influence of the body and soul on each other. Hugon notes that "in respect to the form which the matter had and lost it, matter retains a certain desire, for there always remains a certain proportion between matter itself and its forms; but this is a useless desire because there is no potency to the past; nor is there some natural agent who is able to reproduce the same form in number. The formal reason by which material desires all forms is the substantial being (esse) generated and corrupted, in which all material forms share. This is the common doctrine of the Thomists. Note that this appetite is merely passive, nor can material evolve except by the action of an agent."³¹ This touches evolution ("evolvi materiam").

The human soul after death, separated from the body, is not properly in a natural state, nor in a violent state, but in a state somewhat (secundum quid) natural.³² The separated soul is not properly in a natural state because the human soul is the form of the body, and it is natural for every form to be united with its matter. However, the separated soul is not in a violent state, because the human soul is by its very nature independent of material in being (esse) and operation (operari), and therefore can be separate from the body. The state of separation of the human soul from the body is not according to the nature of the soul as the form of the body, and so can be called praeternatural ("aside" from nature. rather than just natural or unnatural); and since the soul naturally is something that participates in the dignity and operation of separated substances, that state can be called "somewhat (secundum quid) natural."