Nothing in the demonstration shows why the sadness involved in hate or the joy involved in love, should go away if we succeed in getting rid of the idea of the external cause. The key problem seems to be that by removing the idea of the cause of the sadness, one does not remove the cause of the sadness. Thus, the pain may remain even though the idea of its cause is taken away. Bennett suggests that maybe Spinoza has not expressed his thoughts correctly by defining love and and hate in terms of ideas of causes. What Spinoza might have tried to express by the definition of hatred could be a new definition of hatred.
Hatred consists in a bad state caused by the thought of a certain object.
Now, Bennett claims that if separating the thought amounts to displacing the thought from one's mind, then VP2 is alright because if someone gets rid of the thought that is the cause of the unpleasant state, then one gets rid of the unpleasant state as well. The new definition of hate seems to be explicate the nature of hate better than Spinoza's original one. However, I believe that in Spinoza's philosophy of mind, his definition of hate preserves the intuition that the bad state involved in hate must be caused by the idea of the cause of the bad state. What the original definition of hate amounts to is that S hates x if and only if it appears to S that x causes sadness in him. Thus, Spinoza's definition of hate says that S hates x if and only if the idea of x causes sadness in x. Spinoza's definition of hate seems to be equivalent to Bennett's new definition of hate, and this means that Bennett's criticism of the definition is not well-founded.