IDEA, philosophical and psychological term denoting that which is imaged or con ceived in the mind. The word idea has how ever borne very distinct meanings in the his tory of philosophy and psychology. Probably to no other term of the kind have there been attached so many different shades of meaning as to the word idea. Yet what the word signi fies is, of much importance. Till the end of the 17th century, idea had the signification given to it by Plato. The word originally meaning appearance, image, shape, and employed even in philosophy before Plato received and retained from his time a specific sense. With Plato it denotes in the world of things the counterpart of the concept, an immutable essence or being, accessible only to thought. Plato's doctrine of ideas gave stability and objectivity to philo sophical concepts. A bold logical fantasy in Platonism transfers concepts to the external world, hypostatising them into independent es sences standing over against us. The world of thought which thus originates becomes for Plato the core of all reality, the supporter of the world of sense.
Thus it was Plato who won for the term idea the prominent position it holds in the his tory of philosophy.
Originally Greek, the term appears to have passed without change into the Latin tongue. In Greek, as we have said, it seems to have meant appearance, shape or form, whence by an easy transition it acquired the connotation of nature or kind. It is equivalent to ?OK of which it is merely the feminine, but Plato's particularity for this form of the term and its subsequent adoption by the Stoics secured its ultimate triumph over the masculine form. Plato's view comes to this: To the universal notions or concepts which constitute science or general knowledge as it is in our mind, there correspond ideas in the objective world. These ideas are not something indwelling in the indi vidual things, as for instance form in matter, or the essence which determines the nature of the object. Each universal platonic idea has its own separate and independent existence apart from the individual object related to it. It also seems to proceed from or to dwell in some celestial world. There is indeed community be tween the ideas and objects of sense experience. This community consists in participation. The ideas are prototypes, the sensible objects, copies; imperfect imitations of their archetypes.
In the tenth Book of his Laws, Plato dis cusses 10 kinds of motion, reducing them to two kinds. Inasmuch as he regarded the truth or essence of ideas to consist in self-activity as we see it manifested in life and mind, it will be well 'to recall these two modes of motion. The one Plato called °movement through an other)); he called the other movement through self. For him the latter is the origin of the
existence of all being and all change. And it is precisely here that we find Aristotle in agree ment with Plato. The former arrives at the same thought and calls it obaia but retains idea, Greek Mos for "species,)) using aentel to convey the notion of the uself-active cause of life.) For Plato the ideas were inde pendent sovereign forms. In post-classical Hellenism, we find Philo of Alexandria using idea to denote the thoughts of the Divine Spirit. Accordingly we here not only have a unity as a source of all multiplicity, but the whole of reality is supported and spiritualized by a uni versal Soul. Likewise, mighty movements were introduced by the fact that the powers mediating between the Deity and mankind were combined into the unity of the Logos or World Reason, the first-born Son of God. Even with Oriken the essence of reality consists of an in visible world of ideas. Thenceforth the doc trine becomes a constituent element in Christian speculation; and material being originates sub sequent to this invisible world, and continually requires its constituting and animating power.
From Descartes onward usage has become confused and inconstant. John Locke in par ticular ruined the term for English philosophy, where it has ceased to have any recognized definite meaning. He tells us: °Whatsoever the mind perceives in itself, or as the immediate object of perception, thought, or understand ing, that I call idea.° He says further that he has used the term to express whatever it is which is meant by phantasm, notion, species or whatever it is which the mind can be employed about when thinking. In fact, with Locke, idea appears to denote indifferently a sensation, a perception, an image of the imagination, a con cept of the intellect, or emotional feeling, and sometimes the external material object which is perceived or imagined. Yet in spite of Locke the word was used in the Platonic sense in literature as well as in philosophy till the 17th century. Examples in literature are to be found in Spencer, Shakespeare, Hooker and Milton. Thus in 'Paradise Lost): " God saw his works were good. Answering his fair idea." The fortune of the word idea is curious enough. Employed by Plato as described above it stands in lofty contrast to the unreal images of Plato's sensible world. But it was lowered by Descartes Who extended it to The objects of our consciousness in general. And when, after Gassendi, the school of Condillac had analyzed our highest mental faculties into our lowest, idea was still more degraded from its Platonic position. °Like a fallen angel, it was relegated from the sphere of Divine intelligence to the atmosphere of human sense. . . .)) (Hamil ton).