 The appeal to individuating essences accounts for the robust persistence of bodies. In IIIp6 Spinoza says that “Each thing, as far as it can by its own power, strives to persevere in is own being”. In arguing for this conatus doctrine, Spinoza states that “singular things” are that “by which God's attributes are expressed in a certain and determinate way, i.e., things that express, in a certain and determinate way, God's power, by which God is and acts”. “Things” here takes the active position. Things express power; they do the expressing. They are not mere expressions of it. Power is expressed by things, rather than merely through them. Because this is an active expression of power, the thing not only persists through externally caused changes, but opposes those changes which would tend to destroy it, i.e., to keep it from expressing God's power in the way which constitutes its essence. Finally, in IIIp7, Spinoza expressly identifies this striving with the thing's essence; “the striving by which each thing strives to persevere in its being is nothing but the actual essence of the thing.”