Forms exist neither in space nor time, they can be known only by the intellect, not by the senses, the forms have greater reality than ordinary objects observed by the senses. . According to Plato true knowledge means abandoning the senses and understanding this "eternal world of forms".
He also states that ideas derived from sense experience have, at some part, a degree of probability, but they are by no means certain. This sounds as though he is second guessing himself and that he admits that there is some knowledge to be gained from the material world. I believe that knowledge is gained through our senses and that natural science plays a key role in the learning and understanding the world around us. Plato is saying that our knowledge is cut of from the world of experience. "His idea that things that can move and change are cognitively unreliable, and cannot be known, has the consequence that natural science is impossible!" (S. Marc Cohen). Take evolution for example, a theory believed by many scholars around the world that over a long period of time various plant and animal species branch off to become entirely new species. Plato says that both commonsense observations and the propositions of science are opinions only. Another argument I have towards the theory is that who is responsible for creating these forms, are they not susceptible to opinion? Who is to judge that these forms are true perfect representations of the objects in the material world?.
Plato was absorbed to find an answer to how we apply a single word or concept to many different objects. Let us take for example, how can the word chair be used for all the individual objects in the physical world that are chairs? I think Plato answered this question correctly by saying that various things can be called by the same name because they all have something in common. He called this common factor the thing's form. So I agree with Plato in that this solves the problem of how objects in the material world are all distinct, that no two chairs are exactly the same, yet they all have `chairness' in common.