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Constructing the World

Tags: #philosophy #epistemology #metaphysics #philosophy of mind #knowledge #consciousness #ai

Authors: David J. Chalmers

Overview

In this book, I explore the idea that the world is, in a certain sense, scrutable: that there is a compact class of basic truths from which all other truths can be derived, given ideal reasoning. This scrutability thesis is a descendant of Laplace’s thesis that a “Laplacean demon” knowing all physical truths could know all truths, but it avoids problems facing Laplace’s thesis by expanding the class of basic truths to potentially include phenomenal truths, indexical truths, and a ‘that’s-all’ truth, and by weakening the derivation relation from logical inference to a priori inference. The book starts by motivating the scrutability thesis as a potential way to revive the project of Carnap’s Aufbau, showing how it can avoid a number of objections facing that project. It then develops a detailed account of the key notions involved, including a number of variations on the scrutability thesis. The core of the book is devoted to arguments for the thesis. I argue that the thesis holds at least for ‘ordinary’ macroscopic truths about the external world, and then extend these arguments to cover various ‘hard cases’, including mathematical truths, moral truths, and truths about consciousness. The final chapters investigate the nature of a scrutability base, considering what expressions need to be included in such a base, and discussing the prospects for a number of principled scrutability theses, such as the thesis that all truths are scrutable from metaphysically fundamental truths. The book also includes numerous “excursuses” expanding on related topics, including the relationship between scrutability, supervenience, and grounding, the structuralist response to skepticism, and the prospects for constructing Fregean senses from the scrutability framework. Along the way, the book addresses a wide range of issues in epistemology, metaphysics, the philosophy of science, and the philosophy of mind, as well as offering a response to Quine’s famous arguments against the a priori. The book is aimed at professional philosophers and graduate students, but many parts will also be of interest to those working in related disciplines such as computer science, cognitive science, and linguistics. The book defends a sort of philosophical optimism: if the scrutability thesis is correct, then the philosophical truth (or at least a large part of it) may well be within our grasp. Furthermore, the scrutability framework provides new leverage on a number of traditional philosophical problems. I hope that even if some of the book’s specific conclusions are ultimately rejected, the framework and the arguments will help to move philosophical discussion forward.

Book Outline

1. Scrutability and the Aufbau

Philosophers have long pondered the fundamental building blocks of thought. Leibniz believed in a set of simple concepts that form an ‘alphabet of human thoughts’ from which all complex thoughts are constructed. John Locke developed a similar picture, arguing that all our perceptions and thoughts arise from combinations of simple ideas.

Key concept: The alphabet of human thoughts is a catalog of primitive concepts, that is, of those things that we cannot reduce to any clearer definitions.

2. Varieties of Scrutability

The central question of this book is whether the world is scrutable: whether there is a compact class of truths from which an ideal reasoner can infer the truth of all other truths. This question can be framed in a variety of ways. One key framing is in terms of A Priori Scrutability, which asserts the existence of a compact class of truths from which an ideal reasoner can know a priori that if those truths obtain, any other truth obtains.

Key concept: A Priori Scrutability: There is a compact class of truths such that for all true propositions P, a Laplacean intellect would be in a position to know a priori that if the truths in that class obtain, then P.

3. Adventures with a Cosmoscope

To argue for scrutability, I introduce the hypothetical device of a Cosmoscope: a virtual reality device that displays all information contained in a class of basic truths. The Cosmoscope Argument demonstrates that if all ordinary truths are scrutable from a Cosmoscope, they are scrutable from the basic truths themselves. I argue in this chapter that a base containing truths from physics, phenomenology, indexical truths, and a ‘that’s-all’ truth may provide such a base.

Key concept: The Cosmoscope argument:

  1. All ordinary truths are scrutable from a Cosmoscope.
  2. If a truth is scrutable from a Cosmoscope, it is scrutable from PQI.
  3. All ordinary truths are scrutable from PQI.

4. The Case for A Priori Scrutability

One key challenge to A Priori Scrutability is that any knowledge of a scrutability conditional may depend on prior empirical knowledge. I argue that this knowledge plays a non-essential role in justification. The frontloading principle demonstrates that if a conditional belief is justified by some evidence, we can move that evidence into the antecedent of the conditional, and the resulting conditional will be justified without appeal to that evidence.

Key concept: Frontloading principle: If one knows M with justification from E, then one can have conditional knowledge of M given E with justification independent of E.

5. Revisability and Conceptual Change

W. V. Quine has argued influentially against the a priori, holding that any statement can be rationally held true “come what may” given sufficient adjustments elsewhere in our system of beliefs. I respond to these arguments in this chapter by developing a framework for understanding meaning change, inspired by Carnap.

Key concept: If this view is right, it is misleading to speak of the empirical content of an individual statement—especially if it be a statement at all remote from the experiential periphery of the field. Furthermore it becomes folly to seek a boundary between synthetic statements, which hold contingently on experience, and analytic statements which hold come what may. Any statement can be held true come what may, if we make drastic enough adjustments elsewhere in the system.

6. Hard Cases

Carnap held that the meaning of a term can be understood in terms of its intension: a function from possible cases to extensions. To determine a subject’s intension for a term, we can present them with descriptions of various cases and see whether they apply the term to each. These possible cases can be understood as scenarios: highly specific ways the world might turn out. Scenarios can be specified using sets of sentences akin to PQTI.

Key concept: For our purposes, possible cases should be epistemically possible scenarios. Scenarios can be specified by PQTI-like sets of sentences: PQTI for one’s actual scenario, variants on it for scenarios close to home, and sentences using different vocabulary for scenarios of very different sorts.

7. Minimizing the Base

This chapter aims to narrow down the scrutability base to a smaller set of primitives. Using a variety of heuristics, I argue that many microphysical and observational terms can be eliminated from the base, but that some nomic and phenomenal terms appear to be indispensable. This provides support for a scrutability base containing phenomenal, nomic, logical, indexical, and totality expressions.

Key concept: I will argue for the thesis that for all ordinary subjects, all ordinary macroscopic truths are scrutable from PQTI. More precisely: for all subjects s and times t, if s is an ordinary subject at t, and if M is an ordinary macroscopic truth in the context of s at t, then M is scrutable (for s at t) from PQTI, where PQTI specifies s and t.

8. The Structure of the World

This chapter explores a number of principled scrutability theses, each corresponding to a principled constraint on the contents of the base: Fundamental Scrutability, Structural Scrutability, Acquaintance Scrutability, Primitive Scrutability, and Narrow Scrutability. I argue that each of these theses is at least tenable, and that some of them look surprisingly attractive. I also discuss how versions of the scrutability thesis can help to vindicate a broadly Fregean view of meaning and content, by allowing us to define intensions over scenarios that can serve many of the roles of Fregean senses.

Key concept: Generalized Scrutability (and Fregean content): If the scrutability thesis is correct, a Fregean view of meaning and content is viable.

Essential Questions

1. Is the world scrutable?

The central argument revolves around establishing that there exists a compact class of fundamental truths from which all other truths can be derived through a priori reasoning. This is a weaker claim than Laplace’s original formulation, which relied on pure physical truths and logical inference. However, it still captures the essence of scrutability, asserting a fundamental connection between a limited set of basic truths and the totality of knowledge about the world.

2. What constitutes a scrutability base?

The book explores a range of potential scrutability bases, including those focused on physical truths, phenomenal truths, and combinations thereof. The minimal base, according to Chalmers, likely involves a combination of phenomenal, nomic, logical, indexical, and totality expressions. This highlights the importance of both subjective experience and objective laws in our understanding of the world.

3. How can we argue for a priori scrutability?

Chalmers defends the notion of a priori scrutability by arguing that justification for scrutability conditionals is not essentially empirical. He employs the strategy of ‘frontloading’ empirical evidence into the antecedent of the conditional, showing that the resulting conditional knowledge can be justified without appeal to that evidence. This argument suggests that our a priori grasp of certain fundamental truths can indeed provide a foundation for knowledge of a vast array of other truths.

4. How does scrutability relate to Fregean senses?

Chalmers explores the relationship between scrutability and Fregean senses, aiming to show how the former can be used to construct the latter. He defines intensions over epistemically possible scenarios and argues that these intensions can serve many of the roles traditionally attributed to Fregean senses, such as determining reference and capturing cognitive significance. This approach offers a potential way to reconcile Fregean insights with contemporary views on meaning and reference.

5. What about ‘hard cases’ for scrutability?

The book examines a range of hard cases for scrutability, including mathematical truths, moral truths, and truths about consciousness, among others. By analyzing these cases, Chalmers aims to demonstrate the wide applicability of the scrutability thesis and to explore the limits of its potential explanatory power.

Key Takeaways

1. The world may be knowable from a compact base.

If the scrutability thesis is true, a limited set of fundamental truths can serve as a powerful foundation for knowledge. This suggests that knowledge is fundamentally interconnected, and that a deep understanding of basic principles can unlock a vast array of further knowledge.

Practical Application:

In AI development, the scrutability framework could inform the design of knowledge representation systems. By identifying a compact set of fundamental axioms or principles, and designing algorithms for a priori reasoning, one could potentially create AI systems capable of deriving a wider range of knowledge and conclusions.

2. Meaning is best understood in terms of intensions.

The scrutability framework suggests that the meaning of expressions is best understood in terms of their intensions, which capture how they apply to different possible cases. These intensions can be more fine-grained than simple reference, reflecting the cognitive significance of expressions.

Practical Application:

For tasks like natural language understanding and machine translation, focusing on the intensions of expressions, rather than just their referents, can lead to more nuanced and accurate results. By understanding the epistemic profile of an expression, AI systems could better grasp its meaning and usage in different contexts.

The scrutability thesis suggests that there is a close relationship between knowledge and explanation. When a truth is scrutable from other truths, it is also explainable in terms of those truths. This insight can help us to better understand the nature of scientific explanation.

Practical Application:

In the development of explainable AI, the scrutability thesis could serve as a framework for understanding and explaining the reasoning process of AI systems. By identifying the fundamental principles and steps of reasoning used by the AI, one could render its outputs more transparent and understandable.

Suggested Deep Dive

Chapter: Chapter 8: The Structure of the World

This chapter is particularly relevant for AI engineers as it explores the nature of the scrutability base and various principled scrutability theses. Understanding the structure of a potential minimal base and the relationships between different types of scrutability can offer valuable insights into designing knowledge representation systems for AI.

Memorable Quotes

Introduction. 13

An intellect which at a certain moment would know all forces that set nature in motion, and all positions of all items of which nature is composed, if this intellect were also vast enough to submit these data to analysis, it would embrace in a single formula the movements of the greatest bodies of the universe and those of the tiniest atom; for such an intellect nothing would be uncertain and the future just like the past would be present before its eyes.

Introduction. 16

A Priori Scrutability: There is a compact class of truths such that for all true propositions P, a Laplacean intellect would be in a position to know a priori that if the truths in that class obtain, then P.

1. Scrutability and the Aufbau. 43

This brings out a key point: a priori scrutability does not require definability. One might think that for a sentence B to be a priori entailed by a sentence A, the terms in B must be definable using the terms of A. However, this thesis is false.

3. Adventures with a Cosmoscope. 116

Of course the Cosmoscope is a highly fanciful device. But its purpose here is simply to make vivid what an idealized reasoner who entertained the hypothesis of PQI would be able to do.

4. The Case for A Priori Scrutability. 201

This line of reasoning tends to lead to a view on which there are substantive constraints on the rationality of ‘ultimate priors’, that is, credences prior to or independent of any empirical evidence.

Comparative Analysis

This book significantly engages with the ideas of other philosophers, particularly historical figures like Gottlob Frege, Bertrand Russell, and Rudolf Carnap. While embracing the spirit of Carnap’s project in “The Logical Construction of the World”, Chalmers takes a less austere approach, broadening the base of primitive truths and employing a priori inference as the derivation relation. This sets his work apart from strict logical empiricism and positions it within a framework of what could be called “Carnapian rationalism”. The book directly tackles challenges posed by W. V. Quine in “Two Dogmas of Empiricism”, particularly those concerning the analytic/synthetic distinction and the viability of a priori knowledge. Chalmers uses the framework of scrutability to analyze meaning change and defend the notion of a priori knowledge from Quine’s attacks. The book also engages with contemporary discussions on topics like the causal theory of reference, exploring the relationship between scrutability, supervenience, and grounding, offering a structuralist response to skepticism, and examining the possibility of constructing Fregean senses. By setting his project within this broader context and responding to major challenges, Chalmers aims to demonstrate the viability and power of the scrutability thesis.

Reflection

This book makes a compelling case for exploring the philosophical implications of the scrutability thesis. While Chalmers’ optimism about the ultimate knowability of truth may be seen as overly idealistic by some, the framework he presents offers a powerful lens for analyzing a range of philosophical issues. His discussion of idealization and the limitations it imposes is particularly insightful, as is his analysis of the relationship between scrutability, supervenience, and grounding. The exploration of hard cases for scrutability, such as mathematical truths and moral truths, is both thought-provoking and potentially valuable for future philosophical inquiry. However, the book’s reliance on the a priori and the assumption of an “ideal reasoner” may raise concerns for empiricists and those skeptical of traditional philosophical methods. Despite these potential points of contention, “Constructing the World” offers a fresh and rigorous exploration of a foundational philosophical question and provides valuable tools for addressing a range of issues in epistemology, metaphysics, and the philosophy of language, all of which have direct relevance to the development and understanding of AI systems.

Flashcards

What is a scrutability base?

A compact class of truths from which all other truths can be derived through ideal reasoning.

What is the A Priori Scrutability thesis?

The thesis that there exists a compact class of truths from which an ideal reasoner could know a priori that if those truths obtain, then any other truth obtains.

What is a Cosmoscope?

A hypothetical virtual reality device that stores and displays all the information contained in a proposed scrutability base.

What is the frontloading strategy?

The strategy of moving empirical evidence from the consequent of a conditional into its antecedent, demonstrating that justification for the conditional is not essentially empirical.

What are scenarios, and how are they specified?

Highly specific ways the world might turn out, for all we know a priori. They can be specified by sets of sentences akin to PQTI (physics, qualia, that’s-all, indexicals).

What are intensions?

Functions from scenarios to extensions, capturing an expression’s application to possible cases.

What is Fundamental Scrutability?

The thesis that all truths are scrutable from metaphysically fundamental truths (plus indexical truths).

What is Narrow Scrutability?

The thesis that all truths are scrutable from truths involving only narrow expressions.