We can see that Shakespeare communicated many different ideas all throughout Romeo and Juliet. Ideas can be thought of as themes, which are central ideas found in a work. Many themes can be found all throughout Romeo and Juliet, including love vs. infatuation, hatred vs. love, fate vs. choice, and even grudges. But one of the most important themes, the one upon which all action in the play hinges, is intense, violent, passionate, uncontrolled emotions vs. rational thought.
Violent, intense, uncontrolled emotions are presented in both the form of love and hatred. The two feuding families hate each other for unclear reasons. Shakespeare even makes a point of stating in the first prologue that, although the feud is a longstanding one, it had been put to rest, but the present generation of Montagues and Capulets have decided to rehash the old argument, as we see in the line, "From ancient grudge break to new mutiny" (Prologue.3). Therefore, the feud is an example of violent, uncontrolled emotions and its consequence is a great deal of bloodshed, including Mercutio's, Tybalt's, and even Romeo's and Juliet's deaths.
Romeo's and Juliet's love is also depicted as violent, passionate, uncontrolled emotions. It's the type of love that is brought on suddenly and only caused by physical attraction; their love is really more of an intense infatuation than real love. Even Friar Laurence points out that their love is infatuation and hints at the dangers of it in his lines, "These violent delights have violent ends / And in their triumph die, like fire and powder" (II.vi.9-10). If we contrast Romeo's and Juliet's rash, intense emotions with the sense and reason of dramatic foils like Benvolio and Prince Escalus, we can see clearly that Shakespeare's central theme is intense, violent, passionate, uncontrolled emotions vs. rational thought and that one of his intentions is to show the dangers of being guided strictly by rash emotions rather than rational thought.