substantial being, tho terms substanec, essence, and nature in reality stand only for different aspects of the same thing, and the distinction between them is a mental one. Substance denotes the thing as requiring no support, but as being itself the necessary support of accidents; essence projierly denotes the intrinsic constitutive elements by which a thing is what it is and is distinguished from every other; nature denotes the substance or essence considered jus the source of activities. "Nature properly speaking is the essence (or substance) of things which liave in themselves as such a principle of activity (Aristotle, " Metaphysics", 1015a, 13). By a process of abstraction the mind arises from individual and concrete natures to those of species and genera.
A few special remarks must be added concerning htunan nature. This expression may mean some- thing concrete, more or less different in various individuals, or more generally something common to all men, i. e., the abstract human nature by which mankind as a whole is distinguished from other classes of living beings. In both cases it is conceived as including primitive and fundamental characteristics, and as referring to the source of all activities. Hence nature, as the internal principle of action, is opposed in the first place to violence and coercion which are external principles of action and prevent the normal play of human faculties. It is opposed also, but less strictly, to education and cul- ture which at times may be the checking of natural tendencies, at times also their development and per- fection. Education, physical and mental, is not a primitive endowment; it must be acquired and is built upon nature as on its foundation. In this sense habit has been termed a second nature. But al- though education is due largely to external causes and influences acting on the mind and the organism, from another point of view it is also the unfolding of innate aptitudes, and hence partly natural.
As between nature in general and art, so between human nature and education there is no clear dividing line. Natural is also frequently contrasted with con- ventional; language, style, gestures, expressions of feelings, etc., are called more or less natural. This opposition becomes more acute in the theories of Hobbes and Rousseau who lay stress on the antithesis between the primitive or natural state of man and the present social condition due to the contract by which men agreed to surrender their rights into the hands of the common authority.
From the theological point of view the distinctions between nature and person and between the natural and the supernatural orders are of primary impor- tance. The former arose from the dogma of the Trin- ity, i. e., of one Divine Nature in three persons, and chiefly from that of the Incarnation i. e., of the two Natures, Divine and human, in the one Divine Per- son in Christ. The Human Nature in Christ is com- plete and perfect as nature, yet it lacks that which would make it a person, whether this be something negative, as Scotists hold, namely the mere fact that a natiire is not assumed by a higher person, or, as Thomists assert, some positive reality distinct from nature and making it incommunicable.
The faculties of man are capable of development and perfection, and, no matter what external influ- ences may be at work, this is but the unfolding of natural capacities. Even artificial productions are governed by the laws of nature, and, in man, natural activities, after they are perfected differ not in kind but only in degree, from those that are less developed. The supernatural order is above the exigencies and capacities of all human nature. It consists of an end to be reached, namely, the intuitive vision of God in heaven — not the mere discursive and imperfect knowledge which is acquired by the light of reason — and of the means to attain such an end, namely, a
principle which musf l)c added 1o natural faculties so as to uplift them and make llicin capable of know- ing and ri'aching this higher destiny. More specifi- cally it incluflcs an enlightenment of the intellect by a positive revelation of CJod manifesting man's super- natural end and the conditions for obtaining it ; it also implies for every individual the indisjiensahlc help of Divine grace both actual, by which God ilhmiines and strengthens human factdties, and sanctifying, by which human natmc is <'levated to a higher mode of activity. Hence theologians ojjpose the state of pure nature in whiih God could have placed man, to the supernatural state to which in fact man was raised.
II. Nature is frequently taken for the totality of concrete natures and their laws. But here again a narrower and a broader meaning must be distin- guished. Nature refers especially to the world of matter, in time and space, governed by blind and necessary laws, and thus excludes the mental world. Works of nature, opposed to works of art, result from physical causes, not from the actual adaptation by human intelligence. This signification is found in such expressions as natural history, natural philoso- phy, and in general, natmal science, which deal only with the constitution, production, [jroperties, and laws of material substances. .Sometimes also nature is afl-inclusive, embracing mind as well as matter; it is our whole world of experience, internal as well as ex- ternal. And frequently nature is looked upon as a personified abstraction, as the one cause of whatever takes place in the universe, endowed with qualities, tendencies, efforts, an<l will, and with aims and pur- poses which it strives to realize.
The problems to which the philosophical study of nature has given rise are niunerc>iis. All however cen- tre around the question of t!ie unity of nature: Can all the beings of the world be reduced to one common prin- ciple, and if so what is this principle? The first Greek philosophers, who were almost exclusively philoso- phers of nature, endeavoured to find some primitive element out of which all things were made; air, water, fire, and earth were in turn or all together supposed to be this common principle. The problem has per- sisted through all ages and received many answers. Aristotle's primary matter, for instance, is of the same nature in all things; and to-day ether, or some other substance or energy is advocated by many as the com- mon substratum of all material substances. After static unity, dynamic unity is looked for, that is, all the changes that take place in the universe are re- ferred to the same principle. Dynamism (q. v.) ad- mits forces of various kinds which, however, it tries to reduce to as small a number as possible, if not to only one form of energy manifesting itself in differ- ent ways. Mechanism (q. v.) holds that everything is explainable by the sole assumption of movement com- municated from one substance to another. Teleologi- cal views give to final causes a greater importance, and look upon the ends of various beings as subor- dinated to the one end which the universe tends to realize.
If nature includes both mental and physical phe- nomena what are the relations between these two cla.sses? On this point also the history of philosophy offers many attempts to substitute some form of Mon- ism for the Dualism of mintl and matter, by reducing mind to a special function of matter, or matter to a special appearance of mind, or both to a common sub- stratum.
Finally, is nature as a whole self-sufficient, or does it require a transcendent ground as its cause and princi- ple? Is the nalura naiurans one and the same with the naiura naturata? By some these expressions are used in a pantheistic sense, the same substance under- lies all phenomena; by others the nalura naiurans, as first cause, is held to be really distinct from the nalura nalurala, as effect. This is the question of the existence