To be or not to be...that is the question.

To be, or not to be, that is the question:

Whether 'tis nobler in the mind to suffer

The slings and arrows of outrageous fortune,

Or to take arms against a sea of troubles

And by opposing end them. To die—to sleep,

Above is Hamlet in an existential crisis. 

The dualist who holds that human beings are composed of independent substances—“mind” and “body”—is no better off in this regard than is the physicalist, who holds that human existence can be adequately explained in terms of the fundamental physical constituents of the universe. 

Existentialism does not deny the validity of the basic categories of physics, biology, psychology, and the other sciences (categories such as matter, causality, force, function, organism, development, motivation, and so on). It claims only that human beings cannot be fully understood in terms of them. Nor can such an understanding be gained by supplementing our scientific picture with a moral one. Categories of moral theory such as intention, blame, responsibility, character, duty, virtue, and the like do capture important aspects of the human condition, but neither moral thinking (governed by the norms of the good and the right) nor scientific thinking (governed by the norm of truth) suffices.