Reasonable Support

If you, as the writer, are trying to support take a side in an arguement, then you must give reasonable support for your opinion of the arguement. If the writer just saying things like "I think" then it seems like an opinion and does not seem sustainable. If the reason is supported by a fact than it is easier for the reader to agree with you and take your side. Key evidence and supportive facts, and being firm with your side of the arguement, may just be the push the reader needs to be on the writers side.