Plato explains that, whenever a number of individuals have a common name, they have also a common idea or form. For instance, though there are many beds, there is only one idea or form of a bed. Just as a reflection of a bed in a mirror is only apparent and not real, so the various particular beds are unreal, being only copies of the idea, which is the one real bed, and is made by God. Of this one bed, made by God, there can be knowledge, but in respect of the many beds made by carpenters there can be only opinion. The philosopher, as such, will be interested only in the one ideal bed He will have a certain indifference to ordinary mundane affairsp. 122.

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