The "human condition" defines humanity's darker nature. While humanity has the ability to be benevolent, "loving," and "selfless," we also have a recognized darker side ("Definition of The Human Condition," worldtransformation.com). Humanity's darker side, of course, has the capability of being evil, including creating war, committing murder, and even possessing the ability to hate. Hatred and murder are the aspects of the "human condition" that Shakespeare explores most in Romeo and Juliet.
Romeo is one character in which we can see the "human condition" portrayed. Romeo has a great ability to love. He even falls in love very easily, as we see with both Rosaline and Juliet. However, he is also characterized by Shakespeare as being so driven by his emotions that he is rash and impetuous. His emotional drive creates the conflicting actions that we see him especially demonstrate with respect to Tybalt. In Act 3, Scene 1, when Romeo first comes on stage, he is filled with love for Tybalt due to the fact that, unbeknownst to Tybalt, Romeo and Tybalt are now family members. Romeo tries to pacify Tybalt, declaring that he never "injured," or insulted Tybalt, but instead "love thee better than thou canst devise" (III.i.67-68). Romeo's declaration of love shows Romeo's capacity to love as a human being. However, when Mercutio picks a fight with Tybalt, resulting in Mercutio's own death, Romeo's love for Tybalt quickly turns into raging vengefulness. When Tybalt returns on stage, we see Romeo's fury and desire for revenge in the lines,
Alive in triumph, and Mercutio slain?
Away to heaven respect lenity,
And fire-ey'd fury be my conduct now! (123-125)
After Tybalt fled the scene immediately after stabbing Mercutio, Romeo had the opportunity to run away from the fight as well. Romeo knew that the Prince's judgement over Tybalt would have been severe, resulting in Tybalt's death. He could have chosen to let the power of the law take over instead of choosing to avenge Mercutio himself. It is Romeo's rash, impetuous emotionalism that drives him to fury and revenge. Romeo's ability to feel both love and vengeful fury is of course an example of Romeo's "human condition."