It is something people could have differing opinions about.
Explanation:
Debatable claim can be defined as a claim of which people may have differing opinions. If the claim presented in thesis is a fact, which can not be debated upon, then there's no point of it. A debatable claim is a claim on which people generally agree or disagree.
Therefore, a claim to be debatable means that it may have differing opinions of people and some may agree to it and some may disagree.
