Hume's question is about rationality and justification of inductive reasoning. Its core is: Whether and how is universal, necessary and scientific knowledge possible? Feng Qi gives a new and original answer to it by his summing up and absorbing predecessors' positive achievements. In his opinion, people's cognitive ability can obtain scientific knowledge of universality and necessity, and thinking forms provide logical guarantees for acquiring such knowledge. Such guarantees include two aspects. First, the space-time form and logical categories provide a logical guarantee for people's obtaining universally valid knowledge. Second, those basic principles of formal logic and the general acceptance principle of dialectical logic provide as well a logical guarantee for grasping universally valid knowledge.