Final answer:
The philosophical perspective that delves into pessimistic humanism and views human existence through naturalistic lenses, acknowledging profound individual freedom and responsibility, is existentialism.
Step-by-step explanation:
The philosophical perspective that often explores pessimistic humanism and human nature in relation to naturalistic assumptions about existence and man is existentialism. This approach typically considers the human condition to be inherently without meaning, recognizing that any such meaning must come from our own actions and decisions. Existentialists, such as Jean-Paul Sartre, emphasize the radical freedom and responsibility that come with being human, which can be both empowering and deeply unsettling.
This perspective is closely related to concepts like the 'absurd', where the only significance our lives have is that which we ascribe to them, challenging the fixed ethical mandates of traditional moral structures. Rather than a universe with predetermined moral truth, existentialists see a world where moral values are derived from human choices and experiences, leading to a sense of anxiety or even despair over the profound responsibility of freedom.