Mencius said, 'From the feelings proper to it, it is constituted for the practice of what is good. This is what I mean in saying that the nature is good.
'If men do what is not good, the blame cannot be imputed to their natural powers.
'The feeling of commiseration belongs to all men; so does that of shame and dislike; and that of reverence and respect; and that of approving and disapproving. The feeling of commiseration implies the principle of benevolence; that of shame and dislike, the principle of righteousness; that of reverence and respect, the principle of propriety; and that of approving and disapproving, the principle of knowledge. Benevolence, righteousness, propriety, and knowledge are not infused into us from without. We are certainly furnished with them. And a different view is simply owing to want of reflection. Hence it is said, "Seek and you will find them. Neglect and you will lose them." Men differ from one another in regard to them; some as much again as others, some five times as much, and some to an incalculable amount: it is because they cannot carry out fully their natural powers.
'It is said in the Book of Poetry,"Heaven in producing mankind,
Gave them their various faculties and relations with their specific laws.
These are the invariable rules of nature for all to hold,
And all love this admirable virtue."Confucius said, "The maker of this ode knew indeed the principle of our nature!" We may thus see that every faculty and relation must have its law, and since there are invariable rules for all to hold, they consequently love this admirable virtue.'~ James Legge translation via nothingistic.org ~
Go here to read the introductory post to this serialized version of the Works of Mencius.