According to dictionary.com, the adjective arguable has two definitions
- susceptible to debate, challenge, or doubt; questionable: Whether this is the best plan of action or not is arguable.
- susceptible to being supported by convincing or persuasive argument: Admirers agree that it is arguable he is the finest pianist of his generation.
I find that these two definitions are a bit contrary to each other. The first one emphasizes that something is doubtful, while the other means that something is probably convincing. How to distinguish between the two definitions from a sentence? Example from google news (including the adverb "arguably")
Carl Lewis, arguably the world's greatest-ever Olympian, is involved in another running battle – to become a politician.
Here, the appellants have an arguable case that the minister's decision exceeded his jurisdiction