Step 1: Understanding the view on mathematical knowledge.
Hume, a philosopher of empiricism, argued that knowledge is based on experience and is subject to probability rather than certainty. In contrast to rationalists, Hume believed that:
- Mathematical knowledge is based on probability and not absolute certainty, as it deals with human perceptions and inductive reasoning rather than direct empirical evidence.
Step 2: Conclusion.
The correct answer is 2. Hume.
Final Answer:
\[
\boxed{\text{The correct answer is 2. Hume.}}
\]