William Shakespeare started writing plays because he was influenced by classical authors, two of which were Geoffrey Chaucer and Plutarch. He also found inspiration from the Bible and nature.
Chaucer's influence is clearly seen in Shakespeare's works, most notably with Shakespeare's use of iambic pentameter. This is seen as a nod to Chaucer's use of a five-line stress. Also, Chaucer's plays included bawdy humor and interesting characters involved in numerous plot twists. Many of Shakespeare's writings follow this same pattern.
The most obvious example of Plutarch's influence is seen in Shakespeare's famous "Julius Caesar" play. Plutarch's "Lives of the Noble Grecians and Romans" was translated by Sir Thomas North. This translation was Shakespeare's primary source for "Julius Caesar."
The Bible also had a huge impact on Shakespeare's works. A conservative estimate of Biblical references that he used totals 1,200. His writings contain more Biblical references than those of any other Elizabethan playwright. His play "Macbeth" is one of his most famous works and it contains numerous Biblical references.
"King Lear" is one of the best examples of one of Shakespeare's work that reflects nature's influence. Throughout the play, the characters speak about natural elements such as the animal kingdom and heavenly bodies. Uncontrollable elemental forces also appear in the form of fires, hurricanes and thunder.