Explore Blake's development of the concepts of innocence and experience, or the movement of the “contrary states” from the Songs of Innocence and of Experience to The Marriage of Heaven and Hell. Define your concepts, noting how they translate into poetic imagery and pictorial design. Does the Marriage provide a different viewpoint than the Songs on the issue of contraries?

When creating his concepts, Blake essentially had one main idea in mind: he wanted to represent the "two contrary sides of the human soul and human nature." Thus, we have the concepts of innocence and experience. In his poetic collection Songs of Innocence and Experience (1794), Blake writes of the difference between these two concepts and how they can shape a person's identity.
In Songs of Innocence, it's easy for the reader to assume that the narrator is childish, youthful, and pure, and remains blissfully naive and uncorrupted by the heavily industrialized society in which he lives. The speaker is often cheerful and unprejudiced, channeling children's ability to look at the world with no prior judgment clouding their thoughts. However, Blake implies that this only happens because they are still unaware of the darkness that controls our world. This is poetically shown through the image of the lamb. Some analysts agree that Blake used the poetic imagery of the lamb as a symbol for the kind and benevolent Jesus Christ.
In Songs of Experience, on the other hand, Blake writes of the corrupted, impure, aggressive, and dark world of adulthood and introduces the concepts of power and sin. He implies that, as they transform into adults, all humans gradually become aware of the existence of evil and its controlling power. At the same time, however, he implies that even the forces of evil can have a certain beauty to them. He poetically shows this through the image of the "tyger." The tyger is the polar opposite of the lamb, and some believe that the tyger represents the vengeful and spiteful God of the Old Testament.
By using various symbols and allegorical language, Blake tells the readers that experience doesn't truly shatter the concept of innocence; it merely darkens humans' perception of hope and happiness. Essentially, his point was to make people understand that both the lamb (innocence) and the tyger (experience) are a part of one unified system. Our transformation from children into adults is inevitable, but we must use our knowledge and experience to bring that joyful and childish innocence back into our lives and thus achieve the perfect harmonious and balanced state of existence.
Blake further solidifies his point in his book The Marriage of Heaven and Hell, in which he explains that human transformation and progression in life is impossible without the existence of contrary states, or opposites in nature.

Without contraries is no progression. Attraction and Repulsion, Reason and Energy, Love and Hate are necessary to Human existence. From these contraries spring what the religious call Good and Evil. Good is the passive that obeys Reason. Evil is the active springing from Energy. Good is Heaven. Evil is Hell.

Good cannot exist without evil, and vice versa. Blake writes of two types of people, "energetic creators" and "rational organisers," and explains the gradual transition from one type to the other. Thus, I think it's safe to say that The Marriage of Heaven and Hell doesn't really provide a different viewpoint on contraries than that expressed in the Songs of Innocence and Experience.