This chapter reviews the original transactional interpretation as based on the Wheeler–Feynman absorber theory of radiation and demonstrates how the Born Rule for the probabilities of outcomes is a direct physical consequence of the transactional formulation. The chapter also accounts for the nature of “null measurements” and applies the transactional picture to the famous two-slit experiment to gain a better understanding of what it means for the experiment to be “finished” and how transactions illuminate the appearance and disappearance of interference based on the type of measurement being performed.