Today, the human species is collectively confronting a complex existential crisis comprised of a number of diverse elements: political, economic, religious, technological, and environmental. The globalization of information and commerce has revealed to us the universality and interrelatedness of all of these factors. A Treatise of Humanism is an attempt to address the human crisis through an examination of ourselves: our past, our possibilities for a future, our common rational capacity (which should give us hope), and our common human nature. As a philosophy of humanism, this book shares many ideas with existentialism, and it may in fact be viewed as a work of American existentialism, focused on our common human condition and on what we may need to do to continue to survive and to thrive together, not only as a species of life unified through reason but as an interrelated collectivity of unique human individuals.