Plato's theory of Ideas

According to Plato, the material world of the senses is an illusion. The real world, on the other hand, is the realm of Ideas which lies beyond the material world. With this view in mind, Plato claims that "only Ideas are real". The material world, or the world of appearances, is constantly changing. The world of Ideas, however, never changes and is free from the limitations of time and space. As a result, Plato's theory holds that Ideas represent true reality, or the Truth which transcends the relativity of matter.
Whereas the objects of the material world are apprehended by the senses, the Platonic Ideas are apprehended by the mind. The Greek words for Idea and Form are both related to the concept of vision. Thus, Ideas or Forms are things which are seen. However, they are not seen with the physical sight of the senses but rather "by a kind of intellectual vision". The mind which is capable of visualizing the higher realm of Ideas is often equated with the soul.
Beyond words to the Ideas which are embodied in them. Again, words are seen as being representations of the Ideas which are the true source of knowledge. Thus, "behind the words rise the genuine, ideal realities enshrined in the Theory of Forms, which alone are admissible as true objects of knowledge". In Cratylus, Socrates indicates that knowledge cannot be gained from the transitory things which constitute the material world. According to this argument, we cannot say that knowledge exists "if everything is in a state of transition and there is nothing abiding". Pure knowledge belongs to the realm of Ideas, which is beyond change and relativity. Socrates clarifies this by claiming: "But if that which knows and that which is known exist ever, and the beautiful and the good and every other thing also exist, then I do not think that they can resemble a process of flux". Therefore, Plato's theory holds that pure knowledge is to be found in the realm of Ideas rather than in the material world. The Symposium addresses these issues and shows that pure knowledge provides the ability to apprehend the Ideas of Truth and Beauty. The Symposium presents a series of speeches on the God of Love

Jean-Paul Sartre--Existence and Essence

Existence," proclaimed Sartre, "precedes essence." This formula is basic for understanding his view
of human existence and freedom. By emphasizing the negating power of consciousness in relation to
being-in-itself, Sartre interpreted consciousness as a form of being that always seeks to transcend
itself but never fully finishes its task. It seemed to Sartre that we humans move to leave behind what
we have been and to become what we are not. We are always headed somewhere; we are never fixed,
complete, and static. Short of death, there is a perpetual process of negation and a continuous
movement into a future of possibility and uncertainty.
What one will become is indefinite until consciousness determines it. We are what we become more
than we become what we are. In that sense, our existence precedes the formation of our essence.
Sartre identified the negating power of consciousness with human freedom. The fact that we can
move beyond what we are toward that which we are not, he argued, signifies freedom. Whenever we
act freely, there is a sense in which we leave something behind. We negate what we have been to try
to become what we are not. Hence, not only does existence precede essence but, Sartre claimed,
"freedom is existence." According to Sartre, a person's life is characterized by freedom, by choosing
what one will be and how one will see the world one inhabits. The determination of what one is
results from our individual choices and not from a series of determined causes outside of or even
within oneself.
Did Sartre go too far in describing the degree of freedom that men and women possess? Far from
having lives permeated by freedom, most persons feel restricted on every side. Many cannot find
enough food, shelter, or work to make a decent living. Sartre was aware of such difficulties. His
account emphasizes that human existence is always situated in particular times and places, and it is
specified further by the relationships we establish with other persons. Many of these situations are
full of pain and tragedy. Yet Sartre contended that the structure of human freedom remains, because
we keep seeking to make something of ourselves. We may be prevented from achieving what we
want, but, in Sartre's view, any kind of human seeking fundamentally involves the freedom he has in
mind.
Ultimately, Sartre argued, our seeking leads us to try to achieve a complete self-identity in which we
comprehend ourselves totally and are no longer constantly at a distance from ourselves. To
accomplish this task, he contended, would be to become God ("being-in-itself-for-itself"), but no
person can succeed in this undertaking. In fact, Sartre claimed, the idea of God is contradictory (an
outcome that makes his existentialism atheistic), for consciousness excludes self-identity, and self-
identity also excludes consciousness. Consciousness always has the quality of being stretched out
ahead of itself. If you became completely self-identical and unchanging, you would not be conscious
any more. Where our drive to become self-identical is concerned, then, we are forever doomed to
frustration. It is in this sense that human freedom makes our existence "a useless passion."