The paper aims to argue that speculative futures are impacted by past and present experiences, in addition to future possibilities, by analyzing the Speculative Design methodology in the context of human cognition and cognitive biases. Drawing from contemporary literature and case studies on Speculative Design, the paper hypothesizes that despite the potential of Speculative Design methodologies to foster novel perspectives, their present applications may need a more comprehensive approach due to the pervasive influence of cognitive biases. To gain an in-depth understanding of the problem, the study utilizes a qualitative theory triangulation methodology grounded on a literature review. It explores and analyzes theories from diverse fields of knowledge, such as divergent thinking, decision-making in the design process, and micro trends in human cognition, to establish conceptual similarities with Speculative Design. Furthermore, it investigates the relationship between cognitive biases and Speculative Design. Finally, the paper proposes a more holistic way of thinking in Speculative Design as a theory of speculation to address the impact of cognitive biases effectively.