In chapter two, we only consider individual ordering utilities, without considering the interpersonal comparability and cardinality. We use topological methods to study social welfare functions and prove Arrow impossibility theorem. 在第二章中,我们在只考虑个人序数效用,而不考虑个人效用的比较和基数效用的情况下研究社会福利函数,并用拓扑学的方法证明了阿罗不可能定理。