The history of thought experiments is now gaining a great deal of attention, and this is due to the renewed interest of philosophers on the subject. This paper inquires into the history of the philosophy of thought experiments. We name the period to be examined in this paper the "forerun." Its main stakeholders are Georg C. Lichtenberg, Novalis, and Immanuel Kant. We will present and discuss the work of each of them in order to characterize the period, and then reveal parallels and lessons that apply to more recently proposed accounts of thought experiments.Philosophical debate about the nature and function of thought experiments would be impoverished without good historical sources. And while valuable work is being done on the history of thought experiments, a comprehensive discussion of the history of philosophical investigation into thought experiments is still absent in the literature (but see Kühne 2005;Moue et al. 2006). In what follows we take the ªrst steps towards providing a more complete picture of the diverse attempts to shed light on thought experiments.The term "thought experiment" made its ªrst appearance about 200 years ago in 1811. The most proliªc period in the history of the philosophical investigation into thought experiments is the current one, which commenced about 175 years later, more or less in 1986. The lack of focus and direction in the ongoing debate over the nature and usefulness of thought experiments is our main motivation to revisit the history of philosophical investigation into thought experiments. We are conªdent that this enterprise can help to correct some of the shortcomings in current approaches to thought experiments, including a lack of appreciation of the literary features of thought experiments, the normativity of scientiªc instances in assessing the nature of thought experiments, and a ten-