If proposition 'All thieves are poor' is false, which of following propositions can be claimed certainly to be true? Propositions:

The proposition "All thieves are poor" being false implies that it's not the case that every thief is poor. But, this logically allows for some thieves to be poor while others are not.

Option 1: Some thieves are poor: If the initial proposition is false, then it's possible that some thieves are rich and some are poor. So, this option could be true but not definite.

Option 2: Some thieves are not poor: If the initial proposition is false, some thieves can be non-poor. So, this option is also a possibility.

Option 3: No thief is poor: This statement directly contradicts the given proposition being false. If some thieves can be non-poor, then not all thieves can be poor. So, this option is definitely not true.

Option 4: No poor person is a thief: This option doesn't directly address the original proposition about thieves. It focuses on poor people. Even if there are poor people who are not thieves, it doesn't necessarily mean thieves cannot be poor. So, this option is uncertain with the given information.

Hence the correct answer is Option 2: Some thieves are not poor