پیوند زنجیرۀ استدلال و مسئلۀ ناهمسنجگی نظریه‌های علمی

This article delves into Dudley Shapere’s approach to addressing semantic incommensurability, focusing on the “chain of reasoning connection.” We will start by reviewing the concept of incommensurability and its various types. Then, we will take a closer look at semantic incommensurability. Before examining Shapere’s solution, we will explore his thoughts on the history and philosophy of science. To understand the chain of reasoning connection, we introduce the traditional theory of meaning and the causal theory of reference and Shapere’s criticisms of them. We will investigate how reasoning chains originating from existing theories can create a connection between them and alternative theories, potentially bridging the gap between their terms. Shapere suggests that two distinct usages of a term in existing and new theories are linked through a chain of reasoning. While some or all descriptions may alter in this process, all changes are traceable through reasons. Lastly, we will present two historical examples that illustrate the challenges faced by the chain of reasoning solution. Shapere emphasizes that a chain of reasoning links existing and new theories to prevent incommensurability. However, issues arise when a new theory emerges from a rejected one. We will present a case in the history of optics. Also, we will demonstrate that the “chain of reasoning” solution to semantic incommensurability relies on scientific consensus and challenges its efficiency by presenting a case in the history of chemistry. Finally, we will highlight how Shapere’s argument is an obstacle to identifying concept relations in a theory or paradigm.
 
Introduction
In this paper, we will discuss Thomas Kuhn’s idea about the incommensurability of scientific theories. There are three types of incommensurability: observational, methodological, and meaning or semantic incommensurability. We will focus more on the meaning or semantic incommensurability in this article because of its significance in Kuhn’s latest work. Meaning or semantic incommensurability occurs when a change in scientific paradigm leads to alterations in the language and meaning of scientific terms. Terms and concepts that have specific meanings within one paradigm may acquire new, potentially incommensurable meanings in another.
We will introduce the later works of Thomas Kuhn. In his latest work, Kuhn stated that meaning incommensurability arises among certain terms in competing theories or paradigms. Philosophers and historians of science have extensively responded to Kuhn’s theory in The Structure of Scientific Revolutions and the controversial issue of the incommensurability of scientific paradigms. Among them, American philosopher Dudley Shapere has endeavored to find a resolution to this issue. This article presents his perspectives on these subjects and then discusses his proposed solution for the issue of meaning or semantic incommensurability. Shapere suggests that by tracing the “chain of reasoning” that leads to changes in the meaning of vocabularies in scientific theories, the problem of meaning incommensurability could be resolved.
In this paper, we present three critiques of his argument or solution for the problem of meaning incommensurability. We provide two historical cases in science that demonstrate how the chain of reasoning in some instances cannot hinder the issue of meaning or semantic incommensurability. The third critique challenges the argument against essentialism, emphasizing that Shapere’s position overlooks the vital role of structural or essential properties in influencing the connections between scientific concepts within a specific theory or paradigm.
Body
In the introduction, we examine Dudley Shapere’s views on the philosophy of science, particularly his solution to the problem of meaning or semantic incommensurability. Shapere’s philosophy of science is based on two principles from the history of science: ”rejecting the possibility of predicting nature” and “principle of scientific internalization.” According to Shapere, scientific development is unpredictable, and he rejects any presuppositions about the evolution of scientific research. He emphasizes the internalization and autonomy within the scientific enterprise, suggesting that science gradually modifies its methods and concepts. This process allows for the revision, modification, and abandonment of methodological and substantive concepts within science. Shapere avoids presenting a general presupposition for the scientific activity that impedes explaining changes and developments in science. He considers changing or abandoning theories as a gradual process rather than a revolutionary one. Shapere argues that reasons create a link between the concepts and structures of existing and alternative theories, allowing for commensurability between the concepts of both. He criticizes both the traditional theory of meaning and the causal theory of reference. Shapere posits that supposing essential properties for concepts is the key factor in the emergence of the problem of incommensurability. He advocates a view that focuses on descriptions rather than on the reference, but none of these descriptions are essential or distinguished. Shapere suggests that two distinct usages of a term in existing and new theories are linked through a chain of reasoning. While some or all descriptions may alter in this process, all changes are traceable through reasons. This enables commensurability in meaning.
Discussion
As noted in the previous section, two critiques are historical case studies, and the third critique addresses Shapere’s arguments against essentialism.

Shapere’s argument emphasizes that a chain of reasoning links existing and new theories to prevent incommensurability. However, issues arise when a new theory emerges from a rejected one, leading to disconnected chains of reasoning and incommensurability. For instance, in the 17^th century, Newton’s particle theory clashed with Huygens’s wave theory in explaining light's nature. Newton’s theory became dominant in the 18^th century, but a paradigm shift occurred in the 19^th century with Thomas Young’s experiments, leading to the acceptance of Huygens’s wave theory. Notably, the alternative theory did not originate from the existing dominant theory but from a previously rejected theory.
The “chain of reasoning” solution to semantic incommensurability relies on scientific consensus. When scientists accept a new theory, it bridges the gap between old and new concepts. However, disagreements within the scientific community can lead to the rejection of the “chain of reasoning,” hindering the transition to new theories. This is illustrated by the contrasting views of Joseph Priestley and Antoine Lavoisier on a newly discovered gas. Priestley saw it as “dephlogisticated air,” while Lavoisier identified it as oxygen. This difference in reasoning led to semantic incommensurability between their theories.
Shapere proposes that the meaning of a concept is composed of a set of characteristics or properties. Changing the meaning of a concept involves adding or dropping one or more properties based on a reasoning process relevant to the problem at hand. These properties are not essential or necessary. Shapere acknowledges that some properties (structural properties) of natural entities are more prominent than others, but this does not mean they are essential or necessary. However, even though these properties can change, it is done through a chain of reasoning. Therefore, the change in the meaning of concepts by adding or removing a property is not considered a revolutionary change in meaning. Consequently, changes in the meaning of both new and old concepts will not cause semantic incommensurability.

However, structural or essential properties are crucial as they establish hierarchical relationships among concepts and related examples. Change of core properties or inherent features can lead to semantic incommensurability, even if there is assumed continuity through a reasoning chain.
Conclusion
In this paper, we reviewed the meaning or semantic incommensurability problem in Thomas Kuhn’s works and then surveyed Dudley Shapere’s response to this issue, specifically his work The Chain of Reasoning, which is based on his perspective on the philosophy and history of science. As demonstrated in the final section, certain historical scientific cases do not align with Shapere’s framework regarding scientific evolution and his proposed resolution for the meaning or semantic incommensurability problem, leading to a resurgence of this issue. Furthermore, our analysis indicates that the refusal to acknowledge the existence of essential and intrinsic characteristics for concepts does not impede semantic incommensurability.