 Now according to Wolff all sensible properties of bodies should be considered as secondary (or mind-dependent) qualities. In §144 of his Cosmologia, Wolff writes: “…extension is a phenomenon in the same sense in which color is accustomed to be called a phenomenon…”. And somewhat later in this same work, he states in §298: “[t]he force of inertia is called a phenomenon in the same sense in which all sensible qualities are called phenomena”. Perhaps the best way to understand Wolff’s view of sensible properties is to consider a quick comparison with Locke’s corpuscularian view of bodies. For Locke, the primary qualities of bodies, such as extension, solidity, shape, size and texture give rise to the secondary qualities that we perceive in bodies, such as color, sound, taste, smell and temperature. According to Locke, secondary qualities are nothing in the objects themselves but are the result of certain “powers” inherent in the primary qualities of things which effect various sensations in us, such as the sensation of a certain color or temperature. Thus it is by virtue of a body’s micro-structure that we are able to perceive its secondary qualities. Wolff, for the most part, accepts this causal-corpuscularian theory of secondary qualities. However, unlike Locke, Wolff believes that all sensible properties are secondary qualities that result from a body’s atomic structure. In very simplistic terms, sensible properties are for Wolff what color, sound, taste, smell and temperature are for Locke. For both philosophers, secondary qualities are phenomenal and mind-dependent properties having their causal origin in some objective (i.e., mind-independent) reality. For Locke, this reality is the independently existing corpuscles that comprise the material world; and for Wolff, this reality is the unextended points of force, or simple substances, that occupy his atomic level cf. Cosm. §191).