 This is the justificatory argument as interpreted in this  article.[8]  We assume the causal principles are true of whatever suddenly appears to exist; to do otherwise would be to contradict what we are naturally inclined to believe.  This is psychologically impossible but epistemically unwarranted. We need only this natural inclination and the series of sensations arising and perishing in consciousness to form beliefs with regard to the continued, external, and independent existence of objects perceived by sense. Causal reasoning provides an accessible reason to assent to these beliefs; so the system comprises existential beliefs that come up to the standard of rationality Shepherd endorses. In addition, causal reasoning about the existence of objects of various kinds provides opportunity to assemble evidence which makes it highly probable that human beings other than oneself exist and objects such as apples and fires exist. As it happens, the opportunity has been largely realized in our experience so far. This enables us to make reasonable predictions about the qualities that things of various kinds will exhibit on the basis of observing only a few of their qualities. This has the considerable merit of allowing us to plan and act with reasonable confidence. Causal inference also produces and provides reason for belief in an almighty deity and the comforts that brings.  These advantages justify beliefs produced by the natural, practically unavoidable assumption of CP and CPI. These advantages are all the more striking in view of fact that Hume’s theory of belief in the external world has none of them and the epistemologies of Reid, Brown, and Stewart lack at least one of them. 