This chapter develops and analyzes how thought experiments connect thinking with actuality. Superficially, imaginary constructions are mere possibilities that diverge from actuality. However, Kierkegaard also characterizes thought experiments as a kind of experience, providing concrete, fulfilling content for an otherwise empty concept – that is, providing what Kant calls a “synthesis” between thought and experience. Two Ages shows how the work of synthesis can begin from observations and move toward understanding or from understanding toward fulfillment in experience. In Works of Love, I propose, we find material for a basic taxonomy of thought experiments that distinguishes them by whether the thought experiment offers cognition of (a) objects or (b) concepts and whether it (a) proceeds from existing concepts or (b) guides the reader in gaining new ones. This taxonomy mirrors Kant’s distinctions between constitutive and regulative concepts and determining and reflecting judgments. It also anticipates the proposals of recent rationalist accounts of intuition that thought experiments provide nonsensory presentations.

This chapter proposes that thought experiments are a cognitive apparatus and situates this view among contemporary accounts of thought experiment. I set forward the project of the book, which is to (1) propose a new account of thought experiments as a method and (2) trace the historical foundations of the term and concept of “thought experiment” from Kant through Ørsted to Kierkegaard. I define “cognition” [Erkenntnis] for Kant as a synthesis of concepts with intuitions and propose that Kierkegaard, like Kant and Ørsted, views thought experiments as useful for achieving cognitions. I introduce the term Tanke-experiment in Kierkegaard and suggest why it has been little emphasized by Kierkegaard scholars and remains widely unacknowledged in contemporary descriptions of the history of thought experiment.

This chapter analyzes Stages on Life’s Way as an extended thought experiment. Though it has some similarities with a literary work of art and is sometimes called a novel, I distinguish extended thought experiment narratives like Stages from literary novels. I will show how Stages, like Repetition, embodies and develops Ørsted’s core elements of variation, active constitution, and the pursuit of genuine thought. I will also contrast Stages as a “psychological experiment” with the field of empirical psychology emerging in the 1800s. Against increasing interest in empirical observation, Kierkegaard’s thought experiments direct attention to what is not outwardly observable.

Kierkegaard and Ørsted were not just contemporaries but personally knew each other. In this chapter, I argue that Kierkegaard probably learned the term Tankeexperiment from Ørsted. This chapter contextualizes Kierkegaard’s use of “imaginary construction” (Experiment) in his work as a whole, including his well-known uses of paradoxes. I will show how the core elements of Ørsted’s account – thought experiment as a method of variation, the need for free and active constitution, and the use of thought experiments for facilitating genuine thought – are echoed in Kierkegaard’s discussions. Along the way, I will describe some decisions on how to translate Experiment and Tankeexperiment that are unfortunate in some ways and fortuitous in others, as I will explain. In these ways, Kierkegaard indirectly takes up Kant’s proposal that “construction” (i.e., Experiment in Danish) is a means of achieving cognition.