The obvious answer would be that Romeo and Juliet do not behave sensibly in Romeo and Juliet, but there are nuances that can be explored. Before going into the question, it may be helpful to look at the definition of the word "sensible":
- having or showing good sense or judgment
- designed to be comfortable, useful, etc., rather than stylish (Merriam-Webster)
It can obviously be argued that Romeo and Juliet do not show good sense or judgment, as they rush quickly into their relationship. This impatience costs both families lives, including the lives of Romeo and Juliet. Many lives would have been saved if Romeo and Juliet took a different route and been more patient in the play. However, Romeo and Juliet's ages must be taken into consideration. Both of these characters are young teenagers, and their emotions are quite sensible for their immature ages. Furthermore, marriages were often quick and arranged during this time period. To a contemporary audience, Romeo and Juliet are humorously quick in advancing their relationship. Yet, their relationship exists in a classical framework, when relationships were extremely different than they are today. When taking their context and ages into consideration, it could be argued that Romeo and Juliet did behave sensibly and to the best of their cognitive ability.