Few interpreters of Berkeley's texts have taken an interest in the status of the animal in his work, which is easily explained by the fact that Berkeley himself hardly seemed concerned by it. Yet Berkeley's conception of the animal is not without its difficulties, which even some of his eighteenth century readers were already to notice. Andrew Baxter, for instance, in his Enquiry into the Nature of the Human Soul of 1733, wonders whether Berkeley's immaterialism must not necessarily lead to a denial of the capacity of any animal to perceive exterior objects, since perception supposes a reflective activity of the mind and Berkeley seems to deny any such activity to animals.