This article introduces Homo Putans, the "supposing human," as a novel philosophical framework for understanding human existence. Supposing, distinct from mere thinking or imagination, involves hesitation, doubt, and a creative engagement with possibilities. It is characterized by its ability to confront ambiguity and construct meaning in the face of uncertainty. The proposed concept, "supposing," is examined as both a cognitive and philosophical act that bridges the gap between uncertainty and understanding. Drawing on historical and contemporary philosophical traditions, including Hans Vaihinger's Philosophy of As If and phenomenological insights from Husserl and Brentano, the study situates supposing as a significant process in human cognition and meaning-making. While rooted in philosophical inquiry, the article also considers conceptual alignments with cognitive science to explore how supposing shapes perception and decision-making. By thriving in ambiguity, supposing is framed as an act of constructing potential realities and engaging with the unknown.