 Positive arguments for attributing beliefs to (at least) human infants and non-linguistic mammals have tended to focus on the general biological and behavioral similarity between adult human beings, human infants, and non-human mammals; the intuitive naturalness of describing the behavior of infants and non-linguistic mammals in terms of their beliefs and desires; and the difficulty of usefully characterizing their mental lives without relying on the ascription of propositional attitudes (e.g., Routley 1981; Marcus 1995; Allen and Bekoff 1997; Zimmerman 2018).