He wrote in a very simple way but with the use of symbolism: each natural element has a symbolic meaning and the poet is the only person that could explain the meaning of the symbols. Blake is also famous for the theory of the “complementary opposites”, with this philosophical idea he would underline the importance of the existence of the opposites like love\hate, good\evil, male\female, because they are necessary for the progress and so they must coexist. These two states coexist not only in the human being but also in the figure of the creator who can be in the same time the God of love and the God of violence. During Enlightenment we have the exaltation of reason, while in preromantic period we have heart, feelings and the power of imagination. The author considered imagination as the mean through which man could know the world. Only God, the child and the poet have this power of vision and thanks to this power poet created the poetry and therefore he became a sort of prophet because he can understands more deeply the reality rather than the others. Blake was concerned with political and social problems of his time, he in particular tells about the bad conditions of the industrial city. His two masterpiece are the "Songs of Innocence" and the "Songs of Experience". In the 1st collection the poet, the child and the lamb are symbols of Innocence, while in the 2nd collection the experience is the symbol of adulthood, the corruption and the unhappiness.