Charles Sanders Peirce (1839–1914) was a highly original and influential American philosopher, widely considered one of the founders of both pragmatism and semiotics. Despite his significant intellectual contributions, Peirce remained largely unknown and his important writings unpublished before his death. His published output reached around 12,000 pages, while a vast bulk, exceeding 80,000 handwritten pages, remained unpublished, making his true legacy still not fully appreciated. Born in Cambridge, Massachusetts, Peirce was the son of a prominent professor of mathematics at Harvard University, who was also one of the founders of the US Coast and Geodetic Survey and the Smithsonian Institute. Peirce followed in his father’s footsteps by attending Harvard, where he earned BA, MA, and MSc degrees. During his time at Harvard, he formed a crucial friendship with the great American philosopher William James, who would later provide significant support throughout his life. However, he also made an enemy of Charles Eliot, who later became president of Harvard and effectively blocked Peirce's chances of employment there. From 1859 to 1891, Peirce was employed by the US Coast and Geodetic Survey. By his own account, he was not a diligent employee, using his time to pursue his own intellectual projects. Tragically, Peirce never held a tenured university position, his only academic appointment being a part-time lectureship at Johns Hopkins University for several years. This lack of a stable academic platform, combined with his unsystematic writing and publishing habits, led to a slow and uncertain dissemination of his ideas. In critical theory, Peirce's theory of semiotics has proven to be the most influential aspect of his work, while philosophy has often focused on his theory of logic and his notion of pragmatism. However, Peirce himself always maintained that logic and semiotics were inseparable, as he believed that thought could only take place through signs. Peirce's pragmatism, later termed "pragmaticism" by him to distinguish it from other emerging interpretations, was a central focus of his thought. While William James is credited with coining the term "pragmatism," he attributed the core concept to Peirce. Pragmatism, as Peirce conceived it, is distinguished by its interest in how things work and its emphasis on belief as an effective mode of thought, as we act on beliefs even without complete verification. Peirce argued that "thought in action has for its only possible motive the attainment of thought at rest; and whatever does not refer to belief is no part of thought itself". He further stated that "the essence of belief is the establishment of habit," or "the establishment in our nature of a rule of action," concluding that "the whole function of thought is to produce habits of action". By 1905, Peirce had generalized this understanding of habit formation, linking beliefs as rules for action, into a metaphysical view of reality itself, including the laws of nature. He argued against accepting the laws of nature as brute facts, insisting on an explanation for their specific values. His explanation was evolutionary, suggesting that "the laws of nature are still in process of evolution from a state of things in the infinitely distant past in which there were no laws". In this view, any determinate thing, action, or belief is ultimately the result of an infinite process originating from this indeterminate past, a past characterized by chaos and a lack of consistent habits. This evolutionary process, Peirce believed, proceeds according to the principle of "generalizing tendency," or "the great law of mind, the law of association, the law of habit taking," leading him to the hypothesis that "the laws of the universe have been formed under a universal tendency of all things toward generalization and habit-taking". This perspective aligns with what has been termed Peirce's "infinite pragmatics". He viewed reality itself as a "supertask," a process of becoming more and more existent, presupposing an infinite continuum, not of discrete points but as a fundamental continuity from which definiteness emerges through "brute acts" that introduce discontinuity, like drawing a line on a blackboard. Peirce's theory of semiotics also involved an elaborate taxonomy of the components of a sign. His work in this area has profoundly influenced diverse scholars such as Gilles Deleuze, Umberto Eco, and Julia Kristeva. Deleuze, for instance, found Peirce's theory of signs to be suitable for conceptualizing the images introduced by Henri Bergson in _Matter and Memory_. Deleuze's interest in Peirce was partly a consequence of the early influence of Wahl, who referenced Peirce's work. Wahl especially noted Peirce's probabilistic "tychism," which suggests that "chance explains regularity itself". This concept of "tychism" also accounts for Deleuze's passing reference to Peirce in his work on Francis Bacon. Another significant contribution of Peirce was his concept of "abduction," which he proposed to explain the growth of knowledge. He argued that to understand how we develop theories, we must assume that "man’s mind has a natural adaptation to imagining correct theories of some kinds," guided by a principle of "abduction" that "puts a limit on admissible hypothesis," akin to an "instinct" developed through evolution. Peirce believed that innate limitations on the hypotheses we can form are essential for successful theory construction, and that the "guessing instinct" uses inductive procedures mainly for "corrective action". He pointed to the rapid progress in early science as evidence that humans possess an inherent capacity to arrive at correct theories relatively easily. Peirce suggested that the search for the principles of abduction leads to the study of innate ideas, which provide the instinctive structure of human intelligence. He even speculated that "nature fecundates the mind of man with ideas which, when these ideas grow up, will resemble their father, Nature," implying that we are naturally equipped with some true beliefs due to the universe's uniformities and the mind being a product of nature. Despite its importance, Peirce's concept of abduction was not widely developed by others in his time. Peirce also had a distinct perspective on truth. He viewed the pursuit of truth as a technical art involving logic, grammar, and rhetoric. For Peirce, truth is not inherent in the initial encounter with signs but is attained through the skillful handling of signs, leading to settled truths. He developed a "trivium" of approaches to truth: the logic of the sign to assess the validity of reasoning, speculative grammar to study modes of signifying, and speculative rhetoric to complement the other two. In contrast to Deleuze's view of truth in signs as a dynamic process of becoming and a disturbing encounter, Peirce’s pragmaticism aimed at achieving truth after engaging with signs through a refined "technical art". In his 1868 essay, "Questions Concerning Certain Faculties Claimed for Man," Peirce critically examined philosophical assumptions about human cognitive abilities, particularly the supposed capacity to distinguish between intuition and cognition. He argued that all cognitions are, in fact, determined by previous cognitions, challenging the notion of a truly primitive, unquestioned intuition. Peirce's ideas significantly influenced William James, his friend and colleague at Harvard. James enthusiastically adopted and popularized Peirce's pragmatism, elaborating on its implications, particularly concerning the concept of truth and its usefulness. James examined truth in terms of its practical consequences and its ability to provide valid explanations or insights. Bertrand Russell, though critical of some aspects of pragmatism, recognized Peirce as a "great American mathematician and physicist and, I believe, one of the greatest philosophers of all time". Russell noted Peirce's early questioning of the deterministic implications of Newtonian physics, even while believing in its fundamental truth. Noam Chomsky also found Peirce's work on the acquisition of knowledge and the concept of abduction to be particularly interesting and somewhat neglected. Chomsky highlighted Peirce's argument for innate limitations on admissible hypotheses as a precondition for successful theory construction. Despite his profound and diverse contributions, Charles Sanders Peirce remained a figure of relative obscurity during his lifetime. It was left to his friend William James to bring his innovative thinking on the relationship between reason and truth to a wider audience, transforming it into a significant force in American and European philosophy. His ideas continue to be explored and appreciated, revealing the depth and foresight of one of philosophy's most original minds.