Plato was a philosopher who explored metaphysic, which lead him to believe that behind every concept such as beauty or every object such as trees in the visible world there is an unseen reality - a Form. Therefore, there is a Form of Beauty and a Form of a Tree. Forms can be seen as ideal blueprints for visible earthly examples of beauty and trees, which Plato calls Particulars, which only appear to exist and are pale reflections of the infinitely real Forms. Forms exist in their own right in the world of the Forms. They exist separately from their Particulars. The Form of Beauty therefore exists separately from our ideas about beauty.
Plato took a dualist approach, so his Theory of Forms was divided into two realms of existence. The world of sense and experience, where things are mutable, this is the world of appearance-o. There is a world which is outside space and time, which is not perceived through the senses, and in which everything is permanent and perfect, this is the Ideal which exist in the realm of Forms. The empirical world shows only shadows and poor copies of the Forms, and is so less real than the world of the Forms themselves, because the Forms are eternal and immutable, the proper objects of knowledge.
Forms are not made of or dependent upon physical matter unlike Particulars, which are and are therefore changeable and imperfect. Plato saw Forms as the source of all knowledge and as such, the Forms must be eternally consistent and unchanging. Being so would suggest that they are immaterial, which is why they cannot be detected by the senses. The Forms are different from the visible world but they don't relate to it.
Plato believed that we only recognise Particulars because of resemblances they hold to their Forms. Although cats come in different shapes, colours and sizes, they all share something of the Form of the Cat. Since we have some awareness of this in our minds, we can recognise their identity. The same is true with concepts like beauty or equality. We recognise two shapes as being equal because we have some awareness of the Form of Equality. So how can we be aware of the Forms if they are beyond our senses? Plato answers this by saying that every human has an immortal soul that had access to the Forms before it was implanted in the body. Therefore, we have an innate knowledge that can be developed through rational thought. This rational thought enables the soul to recall its memories of the world of Forms.
Plato believed that Forms are all connected to each other in an order of importance, the most important being the Form of Good which is central to the existence of the entire universe. It structures other Forms, giving each its own nature. Without the Form of Good there would be no other Forms. The Form of Good illuminates all knowledge, enabling us to recognise other forms. A philosopher's highest task, according to Plato, is to gain knowledge of the Good because this will lead to full understanding and rational behaviour. True knowledge means abandoning the senses and understanding this "World of forms". To contemplate what we see and realise that it is not real; to try and see the world beyond the imperial information we receive. To seek reason and understanding and to grasp real knowledge and the "Form of the good"
Plato uses the analogy of the cave to explain parts of his theory of Forms. Within the analogy many of the key factors represent something else. The actual cave represents the world we perceive, the world of experience. It acts as a barrier to the truth because our perceptions may be flawed. The prisoners trapped in the cave represent us. We are trapped in the physical world of illusion with our handcuffs being our flawed senses and experiences (culture and upbringing). The shadows represent our experiences/perceptions. The journey out of the cave shows us reaching for the reality of the outside world by escaping from our chains of flawed senses and using our minds. The escaped prisoner represents the philosopher, like Plato himself. Being a rationalist, Plato uses reasoning and his innate knowledge to understand the concept of the Forms. As the prisoner (philosopher) reaches above ground he finds it difficult to see, as he is becoming accustomed to the Forms. The form of good represents the sun, like the good sustains all life on earth. The philosopher’s eyes adjust and he can finally see the knowledge of the Forms, he goes back into the cave to try and share his ideas with the other prisoners. The prisoners (society) refuse to listen and they are ignorant and reluctant to change.
To conclude, the forms are believed to be immutable and eternal, they are believed to be an ideal of something and that we should try to achieve it. Plato emphasised the idea that the forms exist in a perfect world and are not a physical object but instead a ‘soul’. Plato stated that the best people to rule society are philosophers, instead of politicians .this is because philosophers have broken the boundary of ignorance and exposed themselves to the world of Forms. On the other hand politicians rule society with their own selfish interests, instead of the people, as they have nor exposed their minds to the Forms. Philosophers like the prisoner feel like it is their duty to tell people but when they try to, they do not listed as they are blinded by the illusory world.