Re-establishing the distinction between numerosity, numerousness, and number in numerical cognition

In 1939, the influential pschophysicist S. S. Stevens proposed definitional distinctions between the terms 'number,' 'numerosity,' and 'numerousness.' Although the definitions he proposed were adopted by syeveral psychophysicists and experimental psychologists in the 1940s and 1950s, they were almost forgotten in the subsequent decades, making room for what has been described as a "terminological chaos" in the field of numerical cognition. In this paper, I review Stevens's distinctions to help bring order to this alleged chaos and to shed light on two closely related questions: whether it is adequate to speak of a number sense and how philosophers can make sense of the claim by cognitive scientists that numbers are perceptual entities. Moreover, I offer further support to Stevens's distinction between numerosity and numerousness by showing that they are relational properties that emerge through different relationships between agents and their environments. The final conclusion is that, by adopting Stevens's distinctions, numbers do not need to be seen as perceptual entities, since the so-called number sense is better described as a sense of numerousness.