The Greek concept of form precedes the attested language and is represented by a number of words mainly having to do with vision: the sight or appearance of a thing. The main words, εἶδος (eidos) and ἰδέα (idea)[7] come from the Indo-European root *weid-, "see".[8] Both words are already there in the works of Homer, the earliest Greek literature. Equally ancient is μορφή (morphē), "shape", from an obscure root.[9] The φαινόμενα (phainomena), "appearances", from φαίνω (phainō), "shine", Indo-European *bhā-,[10] was a synonym. These meanings remained the same over the centuries until the beginning of philosophy, when they became equivocal, acquiring additional specialized philosophic meanings. The pre-Socratic philosophers, starting with Thales, noted that appearances change quite a bit and began to ask what the thing changing "really" is. The answer was substance, which stands under the changes and is the actually existing thing being seen. The status of appearances now came into question. What is the form really and how is that related to substance? Thus, the theory of matter and form (today's hylomorphism) was born. Starting with at least Plato and possibly germinal in some of the presocratics the forms were considered as being "in" something else, which Plato called nature (physis). The latter seemed as "wood",[11] ὕλη (hyle) in Greek, corresponding to materia in Latin, from which the English word "matter" is derived,[12] shaped by receiving (or exchanging) forms. But what were the forms? In Plato's dialogues as well as in general speech there is a form for every object or quality in reality: forms of dogs, human beings, mountains, colors, courage, love, and goodness. Form answers the question, "What is that?" Plato was going a step further and asking what Form itself is. He supposed that the object was essentially or "really" the Form and that the phenomena were mere shadows mimicking the Form; that is, momentary portrayals of the Form under different circumstances. The problem of universals – how can one thing in general be many things in particular – was solved by presuming that Form was a distinct singular thing but caused plural representations of itself in particular objects.[13] Matter was considered particular in itself. These Forms are the essences of various objects: they are that without which a thing would not be the kind of thing it is. For example, there are countless tables in the world but the Form of tableness is at the core; it is the essence of all of them.[14] Plato's Socrates held that the world of Forms is transcendent to our own world (the world of substances) and also is the essential basis of