natural person (defined)

Here are the exact definitions from Barron's Canadian Law Dictionary, fourth edition (ISBN 0-7641-0616-3):

natural person.

A natural person is a human being that has the capacity for rights and duties.

You will observe that the natural-person has the "capacity" (i.e. ability) for rights and duties, but not necessarily the obligation. The artificial-person has rights and duties that may be attached (i.e. assigned) by laws.