Robert DiSalle: Overcoming Metaphysics from Within Physics: An Optimistic Induction for Empiricists

The speaker reflects on the intellectual contributions to the department and discusses the concept of overcoming metaphysics in physics, particularly through general relativity. This idea challenges the notion that relativity represents a departure from metaphysical views, asserting instead a continuity with Newtonian physics. The speaker criticizes the discredited notion that general relativity is inherently anti-metaphysical.

The discussion focuses on the empiricist perspective on realism in scientific theories. The speaker emphasizes that scientific theories make claims about the world that extend beyond mere observations. Examples from the history of physics illustrate how theories have transcended initial metaphysical interpretations to identify enduring physical connections.

The speaker critiques empiricist misconceptions about the theoretical structures and principles in science. They argue against comparing physical objects to mythical entities, like the gods of Homer, highlighting the empirical basis of theories about atoms and molecules. The evolution of these theories from hypotheses to solid empirical principles is discussed.

Exploring the relationship between mathematical structures and empirical phenomena, the speaker references Reichenbach's difficulties in linking theoretical terms with physical aspects. The history of space-time understanding, from local measurements to broader scales, is examined. The speaker argues against relying solely on mathematical models detached from empirical observations.

The speaker questions the idea that the truth of scientific theories explains their success. Historical attempts to explain science's success through metaphysical frameworks are reviewed, including Cartesian metaphysics, Leibniz's final causes, Berkeley's idealism, and Kantian intuition. The speaker suggests that explaining scientific success often involves metaphysical extrapolation beyond empirical evidence.

The notion of structural realism, associated with Henri Poincaré, is discussed. The speaker clarifies that while scientific theories may evolve, certain relations discovered by previous theories persist. They highlight Poincaré's view that future theories must incorporate these enduring relations, even if the underlying ontological and mathematical structures change.

The speaker emphasizes that successful scientific theories reveal physical connections that future theories must account for. They argue that theories teach us about genuine connections in the world, which are preserved even as ontological and structural frameworks evolve. Examples include Newtonian gravity and its role in understanding orbital dynamics.

Newton's strategy for addressing gravity without delving into its metaphysical causes is highlighted. The speaker explains how Newton distinguished between empirical observations of gravitational forces and their underlying nature. Newton's remarks on central forces and their mathematical treatment underscore his method of separating physical reasoning from metaphysical speculation.

Newton's arguments against Cartesian definitions of motion are revisited. The speaker explains how Newton's understanding of gravitational forces allowed him to reason about planetary motions without relying on absolute space. This approach, emphasizing empirical reasoning over metaphysical assumptions, advanced the study of celestial mechanics.

The speaker discusses Newton's efforts to demonstrate that physical reasoning about forces is independent of motion through absolute space. They explore Newton's corollaries and propositions, which allow for the treatment of isolated systems and the prediction of planetary motions, free from the need for absolute spatial references.

Berkeley's criticism of absolute space, based on Newton's own demonstrations, is examined. Berkeley's empirical approach to scientific reasoning is emphasized, advocating for relative measures and practical calculations over abstract metaphysical ideas. This perspective aligns with the empirical foundations of Newtonian mechanics.

The speaker highlights Berkeley's views on the nature of motion and scientific reasoning. Berkeley's insistence on distinguishing mathematical hypotheses from the nature of things and focusing on relative measures underscores the empirical approach to understanding physical phenomena. This method preserves the practical utility of scientific theories.

The concept of 'blunt instrumentalism' is introduced, describing scientific theories as practical tools for discovering connections in the world. The speaker argues that while these theories extend empirical reasoning, they often break down under extreme conditions, necessitating the development of more sophisticated models. This iterative process advances scientific understanding.

The speaker discusses the evolution of mathematical schemes in scientific theories, using quantum mechanics as an example of a scheme that initially seemed reasonable but ultimately proved inadequate. This process of refining and replacing mathematical models illustrates the progressive nature of scientific inquiry.

The speaker argues for the continuity of structural relationships in scientific theories, even as ontological pictures change. They emphasize that equations representing empirical relationships endure across different theoretical frameworks, preserving the connections discovered by earlier models.

The speaker examines the legacy of Newtonian gravity in modern physics, highlighting the persistence of certain mathematical relationships despite changes in theoretical frameworks. This continuity underscores the enduring empirical connections identified by successful scientific theories.

The speaker concludes by reiterating the importance of empirical reasoning in scientific progress. They emphasize that while theoretical structures may evolve, the core empirical relationships discovered through scientific inquiry remain a fundamental part of our understanding of the natural world.