Plato’s Metaphysics is a dialogue between Socrates and Plato, written in the 4th century BC. The dialog is an attempt to draw out the basic outlines of the fundamental problem of human knowledge, which Plato believed was intractable (though he did not seem to understand this himself).
The dialogue starts with Socrates asking:
Aristotle, who had been a philosopher at Crotona (modern-day Crotone) in Sicily, had previously asked him: So what is the nature of truth? And what is the essence of knowledge?
He replied that there was only one answer — that truth was something that existed — but nothing else. So what is it? And where does it come from? He said there were many answers to those questions, but he thought they would be more informative if we put them on one side for now.
There are many things that are real; some exist independently of us. Some exist in space and time — like trees or stones — and others exist only in our minds. Only this last category has any independent existence; only its true definition makes it real. It exists because we define it as such and because other people have defined it for themselves as such. It may have an extension into space or time; we do not know what extends beyond our minds.
But suppose you think about how you define your own definition. In that case, you will see that you never define anything at all outside yourself… Plato’s Metaphysics Aristotle then tries to explain how knowledge can be justified by appealing to experience. We can know that something exists by having experiences with objects whose properties match those of the object being known… …it follows from this [that] our experience must correspond with the properties of objects existing independently of us… …once again, [we] cannot know anything independently… Facts are not particular instances we can grasp by any particular method or through any particular way of knowing things… Knowledge is universal knowledge: when we have it, we share it; when someone has it, he shares it with everyone else… …This implies that no one knows anything without first learning about everything else…. What this means is quite different from saying that knowledge exists before experience and before perception or inference…. We perceive things by using our senses. They exist in space and time as well as being perceived by them…. If they do not exist independently of us or if they exist only in our minds, then our perception cannot be a reliable guide to them… Our perceptions.
Ancient Greek philosophers were greatly troubled by one aspect of the physical world. The world appeared to them as a kaleidoscopic picture of continuous change or flux. It seemed to be in a state “of constant becoming and continuous change, where things appear to be purely momentary, and in an incessant transition from the immediate past through the present into the future.”
Similarly, there was another problem which is that “perception” and “sensation” of things vary between individuals; and that sometimes the same individual has different perceptions and sensations about the same thing. Objects and things seemed to be “wholly wanting in constancy and stability.”
Many ancient philosophers thought that no reliable knowledge could be had of things in a state of perpetual change. For example, Heraclitus observed that we cannot step in and out of the same river, for it would have changed in the meanwhile (or between our two steps).
However, some philosophers like Protagoras believed that perception or the deliverances of human senses is knowledge of the empirical world as it is.
For Plato’ Metaphysics, the external world, as given in senses, is only an appearance. He uses various expressions to describe the sensible and phenomenal world, such as; the many, the divisible, the becoming, and non-being.
According to Plato’s Metaphysics, the real world is an abstract realm of eternal and unchanging Ideas or Forms. The objects and things of the physical world are appearances or phenomena, which are like images of the Forms in the world of Ideas. Plato calls the Forms archetypes and the objects of the material world their copies.
Plato believes that philosophers gain knowledge of the Forms (or being) through the intellectual perceptions of the soul. Readers may wonder how the above piece of metaphysics ties up Plato’s moral philosophy. To anticipate our discussion, Plato argues that since philosophers have an insight into Forms or reality, they should be the rulers of a State or that, alternatively, rulers should become philosophers.
Bertrand Russell looks from a different perspective at the problem of continuous change in nature which bothered Greek philosophers. They felt that it prevents men from gaining certain knowledge.
According to Russell, the problem which puzzled the Greek philosophers relates to universals or general terms used in language. Examples of general terms are roses, tables, chairs and the like. In modem language, these terms are concepts, and the objects which fall within the definition of any concept are assigned to it. There may be any number of instances of the concept ‘rose.’
Some philosophers believe that there is a form or essence underlying all such instances of a concept. They are called realists. Their opponents are nominalists who argue that one need not look beyond the individual instances of ‘rose.’