Leibowitz and Agassi: Conversations on Philosophy of Science - Part 5

The fifth installment in the fascinating and prolific series "Leibowitz and Agassi: Conversations on the Philosophy of Science" represents an intellectual and philosophical pinnacle, presenting a profound and reasoned discussion on the core issues of scientific inquiry. It serves as a rare window into how two giants of Israeli thought, Yeshayahu Leibowitz and Joseph Agassi, deconstruct and rebuild fundamental concepts of scientific and philosophical thinking, confronting their distinct yet complementary perspectives. The heart of the discussion in this part likely revolves around the question of scientific identity—defining what science is, how we distinguish it from non-science or pseudoscience, and the criteria for the validity of scientific knowledge. These questions touch directly upon the "Demarcation Problem," a central concern for philosophers of science. At the center of the debate are two foundational philosophical concepts that shaped 20th-century discourse on the nature of science: induction and falsification. Induction—an approach famously critiqued by David Hume and later addressed by various logicians—posits that scientific knowledge is built from numerous observations from which general conclusions are drawn. The logical backbone of induction, known as the "Problem of Induction," argues that there is no complete logical justification for inferring a universal law from a finite number of individual observations; there is never certainty that the next case will mirror the previous ones. Conversely, falsification, developed extensively by Karl Popper (whom Agassi regards as his mentor), offers a different criterion for the demarcation of science: a statement is scientific not because it can be verified, but because it can, in principle, be refuted. A scientific theory must be empirically testable in a way that allows it to be proven false. Parenthetically, the discussion may also touch upon Thomas Kuhn, who, in *The Structure of Scientific Revolutions*, proposed a model emphasizing the sociological and historical characteristics of scientific change—paradigms, normal science, and revolutions—a model that often stands in contrast to Popperianism. Professor Leibowitz, as is his custom, enters the discussion with a consistent and uncompromising philosophical stance. He views science primarily as a human activity—an instrument and a method for navigating the world and solving problems—rather than the discovery of an ultimate, transcendent truth, reflecting a distinctly anti-metaphysical approach. He does not believe in the existence of an absolute scientific "truth," but rather in a provisional and functional "correctness." For him, science does not deal with "essence" but with "action"—it examines how things function and occur, developing models for prediction and control without penetrating their inner essence. His sharp and zealous distinction between fact and value (the "realm of facts" versus the "realm of values") is inevitably expressed here: science deals only with the facts of "what is," while the choice of values is an existential and subjective decision that cannot be derived scientifically. In this context, he likely refers to the work of giants like Newton and Einstein not as discoverers of "absolute truth," but as pioneers who developed fertile theories that allowed us to understand and act within the world more effectively until they were replaced by superior ones. Leibowitz emphasizes that scientific knowledge is human, limited, and subject to change, and should never be granted divine or absolute status. He may also reference philosophers like Ernst Mach, whose empiricist and anti-metaphysical approach aligns closely with his own. On the other hand, Professor Joseph Agassi, as a loyal and enthusiastic representative of the Popperian school, staunchly defends the principle of falsification as the heart of science. For Agassi, science is not a repository of verified facts but a constant, critical effort to refute existing theories and seek better ones. He points out that the history of science is filled with refuted theories, and that this is precisely where its strength and progress lie—not in confirmation, but in refutation. Agassi emphasizes the need for perpetual criticism and the ceaseless drive to expose errors. To him, science can be compared to an evolutionary process of "survival of the fittest" for theories; those that withstand the test of refutation survive until they are eventually disproven. He rejects the inductive approach for its lack of logical justification and underscores the unique status of falsification as the primary tool for demarcating science. Agassi highlights the unique character of modern science, which he believes began in the 17th century, distinguishing it from common sense or old philosophical rationality, which he views as insufficiently critical. He might discuss the difference between Popper’s "corroboration"—meaning a theory has survived rigorous testing—and "verification," which Popper rejected. Agassi may also touch upon the concept of "rationality" through a Popperian lens, where rationality is defined as the willingness to remain open to criticism and to change one's position based on evidence. The central tension emerging from the discussion likely lies in the degree of "objectivity" in science and its relationship to "truth." Leibowitz emphasizes the limited human nature of scientific activity, while Agassi seeks to maintain an objective standard—falsification—as a tool for the rational advancement of knowledge. Another question arises: can science offer us "meaning" or "values"? On this, both professors hold similar views: the role of science is to describe and explain the world, not to dictate morality or the meaning of existence. In this sense, despite their differing approaches, Leibowitz and Agassi are alike in their critical temperament, systematic thinking, and aversion to any dogma or authority not subject to scrutiny. Both, in their own way, advocate for independent thought and constant re-examination. The importance of this entire series, and this installment in particular, is not merely academic. it constitutes an extraordinary cultural and educational document in Israel. In these conversations, two world-renowned thinkers strip away the complexity of profound philosophical debates for the general public with clarity, rich and precise Hebrew, and an infectious intellectual passion. They demonstrate critical thinking in action—how to argue respectfully and substantively, and how to analyze fundamental issues beyond passing trends. The series has educated generations of students and intellectuals in original thinking, skepticism, and the rejection of dogmas. It carries a vital message about the importance of science—not just as a body of knowledge, but as a way of thinking, a tool for discovering the limits of our knowledge, and the embodiment of human rationality in all its complexity and boundaries. Part V of the series is therefore not just a brilliant philosophical discussion, but also a national lesson in thoughtful, critical citizenship.

Video transcript