The meaning of the underlined sentence

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Can you tell me the meaning of the underlined sentence? (Specifically I cannot make out what "of which" stands for?)

"But man has almost constant occasion for the help of his brethren, and it is in vain for him to expect it from their benevolence only. [...] It is not from the benevolence of the butcher, the brewer, or the baker, that we expect our dinner, but from their regard to their own interest. We address ourselves, not to their humanity but to their self-love, and never talk to them of our own necessities but of their advantages. Nobody but a beggar chooses to depend chiefly upon the benevolence of his fellow-citizens."

[The above passage is from Adam Smith's The Wealth of Nations, so I thinks there's no problem of copyright infringement.]

The passage exhibits a dual movement characteristic of Smith. On the one hand, there are no motives, even kindness, of which we can say that an appeal to them is an unqualified good. On the other hand, even self-love, may under certain circumstances be not only appropriate, but may indicate moral qualities.