I think that this becomes one of the central issues in the myth of Prometheus.  On one hand, he does sacrifice to help the mortals and he realizes what this sacrifice will entail.  Yet, it is here where I believe that some of the myth's complexity is most evident.  On one hand, he does what he does because Prometheus believes it to be right.  Prometheus believes that the world of mortals and immortals is to be bridged.  It can be argued that Prometheus was a response to the structure that kept mortals at a power disadvantage.  In giving mortals fire, he was able to rectify some of this power disparity.  Another reason why Prometheus did what he did was as a response to Zeus.  The absolutism with which Zeus ruled was something that Prometheus repudiated.  Given the occasional irrationality of Greek divinity, Prometheus might be seen as a self- correcting mechanism and his actions can be seen as a way to right what was wrong.  Finally, it can be argued that Prometheus possessed loyalty to mortality and sought to take care of them in a benevolent manner befitting of divinity. In this vision, Prometheus sacrifices for his people because he recognizes that this is the role of gods to mortality.  In this, Prometheus becomes one of the first of many sacrificial religious figures to whom the utmost in loyalty is warranted.