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Similarity or likeness (Gr. μοίωσις Lat. similitudo ) denotes some agreement between two or more things, something short of absolute identity, a partial sameness, as in "not exactly the same but similar." Thus similarity indicates some shared unity of entities somewhat the same, and similitude means any relative sameness. This article sketches, in successive paragraphs, various uses of the notion in epistemology, metaphysics, patristic theology, and Thomistic theology.

In knowledge, the distinction of the knower and the known is more evident than their relative sameness. Yet a similitude of the thing somehow present to the knower re-presents the thing, and the comparison of the knower's possession and the thing's offering furnishes the known identity called truth. science itself is based on the causality of this likeness as provided by objects and present in subjects, and thus explains how man knows something to be so, and also why it is sosuch explanation also accounting for his certitude. (see epistemology.)

In distinguishing the properties of the basic catego ries of being (Cat. 11a 1519), aristotle shows likeness to be the first feature of quality. With further precision, in the Metaphysics (1018a 1519; 1021a 1014; 1054b 51055a 2) he coordinates "the similar" with the basic traits of all "being," "one," and "same," and thus discloses various degrees of unity. "One" applied to such variations of being as substance, quantity, and quality renders the basic notions of "same," "equal," and "similar," respectively. But since "same" extends beyond things substantially one (or numerically the same: as Plato and "the author of the Timaeus "), a further distinction may be made between things specifically the same (Plato and Socrates), those generically the same (Plato and his dog), and finally, those analogically the same (Plato and Pluto)with greatest identity in the first and the least in the last. Thus, a second view of "similar," under the title of sameness, escapes the limits of the accidental unity of quality to apply to three degrees of relative sameness that depart from the absolute, or numerically self-same. So Aristotle provides two usages: the univocal, based on quality, and the analogical, based on any formal qualification. The latter furnishes the basic intentional unities: species naming similitude in nature or form (disregarding the numerical diversity of individuals); genus denoting a more remote similitude (by prescinding from specific differences); and the analogical unity of those not so obviously alike intrinsically, but manifesting similitude in acting alike or affording a basis for being understood similarly (see analogy).

The Greek Fathers seem to have read with Philo's eyes the creation account of man as made "to the image and likeness" of God (Gn 1.2627; Septuagint εκωνμοίωσις). irenaeus took image for nature, and likeness for grace; origen, with most Platonists, gave image a dynamic character terminating in assimilation to God by likening, thus contrasting image and likeness as beginning and end of human life. This likening by resemblance assumes in St. clement of alexandria the function of grace in Irenaeus, supplying the supernatural perfection lacking to nature. gregory of nyssa sees here two aspects of the same reality: εκόν naming the static terms of beginning and end; μοίσωις giving the dynamic advance from the one to the other, the progressive retrieving of the divine image once had, but lost by sin.

St. thomas aquinas finds image (Summa theologiae 1a, 35) the proper title for the Son; he sees man created to image the Trinity just by being human, in knowing and loving (1a, 93) and fulfilling (1a2ae, prol.) his destiny by assimilation (i.e., with increasing likeness to God) through a life of virtue, aided by the exemplarity of Christ (3a, prol.). The various facets of likeness are brilliantly displayed in the view of beings unequally sharing in the absolute perfection of existence (1a, 4), inherently seeking greater realization of that perfection (1a, 56), and tending toward reunion with their principle (1a, 4246) by imitating their cause (1a, 50.1; 103.4; 1a2ae, 109.6; etc.), with similitude as the cause of love (1a2ae, 27.3) and all delight (32.7). The patterns of similitude measured between model and copy are disclosed in the tracts on ideas (1a, 15) and exemplarity (1a, 44.3); the dynamism of assimilation is seen in C. gent. 3.1921.

See Also: exemplarism; image of god; jesus christ, articles on; relation.

Bibliography: v. miano, Enciclopedia filosofica (Venice-Rome 1957) 4:784786. p. t. camelot, "La Théologie de l'image de Dieu," Revue des sciences philosophiques et théologiques 40 (1956) 443471. c. fabro, Participation et causalité selon S. Thomas d'Aquin (Louvain 1961).

[b. m. mattingly]