The forms are basically different from the visible world as that they are dependent upon physical matter. The forms have to be one hundred percent reliable as they are the source of all knowledge. They are immaterial, as they cannot be detected by the senses. Particulars depend on the physical matter as they are imperfect and can change endlessly, unlike the forms.
Plato explains his theory of forms and ideas concerning the mortality of the soul. We find that the soul and body are separate and that the soul lives after death and had lived before. This leads us to the idea of forms and how we acquire the knowledge of these before birth. The only time the soul is separate from the body is in death. Since the soul can only obtain knowledge of forms when it is away from the body, we understand that after death is the only time when the soul can acquire this information. The intellect loses these ideas of forms when it is born unto a physical body. Although forgotten, the soul still holds this knowledge and what is known as learning is actually remembering, or recollecting, the knowledge we lose at birth. These forms give us ideas of how we should relate objects to one another. For example, we know that a certain colour is red even though it is not a pure red. When we see a red chair we recollect the form of red from our past knowledge of the soul. These forms are abstract ideas that hold true throughout each soul and are something that the physical body can never know. Since we only have an idea of these forms, we can never experience a true form with our senses. Our senses give us an understanding of the physical world at any given moment, but the physical world is constantly changing, so our senses can never let us experience the world as it truly is. Our senses can only let us experience how the world as we know it in a particular moment. The soul acts as a container for this knowledge and keeps it through each bodily life.
One argument against these ideas is that the soul would not be strong enough to survive the destruction of the body. This cannot be true, as the soul directly controls the motions of the body; for the soul can will the body in any way it chooses and may oppose the body at any point. The attunement theory, explains that the soul cannot be destroyed by death. It compares the soul and the body to a string instrument, i.e. a lyre, and when the lyre is destroyed, so is the harmony, as with the body. The harmony of an instrument is a composite thing, which the soul is not. Composites cannot pre-exist their components. When the lyre is destroyed, so is the harmony; however, the soul cannot be destroyed for it is not a composite thing such as harmony, which means the soul, is able to pre-exist its component (the body).
Another argument is that the body may only be clothes for the soul. The clothes will wear out eventually and the creator that made these clothes will also expire at some point. Suggesting that the body is clothes and the soul is a creator, it may be the case that although the soul may exist after death, it may not exist infinitely, and eventually expire. Since the soul can oppose the body, the soul chooses to admit death. If the soul admits death, then the soul may die. If the soul does not admit defeat then the soul is deathless, and if the soul is deathless then the soul is indestructible. Our souls know the concept of the forms, and are the same throughout all souls. Since we cannot change the concept of these forms without creating confusion, all souls must have gotten this shared knowledge when the soul was separate from the body, i.e. death and before life. From this we understand that forms exist and as we learn we recollect these forms throughout our bodily life.
b) How convincing is the theory?
According to Plato "The forms are not concepts in the mind, but are existing realities apart from the mind. The forms are eternal and immutable". Forms are imperfectly reflected in human affairs, and language limits us in how we can explain these forms. The forms are "out there" somewhere. The world from which these forms are described to come from is not one that can be viewed by the human eye but is visible as pattern. We can believe in the existence of ideal standards without claiming to possess them. The belief in an absolute that we do not possess is often the best way to understand the concept of it.
To show, how the theory could be convincing. Every person has an idea of what perfection is, however can never match this perfection. In the theory of forms it states that our souls have been to this place and so we have the knowledge but it lays dormant or unreachable in our minds. This backs up the fact that human perfection can never be matched. Thus making the theory convincing."The forms are not concepts in the mind, but are existing realities" meaning there is another 'world' in which these forms are active and real.
