The objective behind academic writing is to make claims about different things in the world that exist or they should exist. When we talk of PhD work, it holds true here also. Whether your thesis deals with qualitative or quantitative research, it holds true. However, when you make a claim in your ‘PhD thesis, it does not hold much relevance if the readers aren’t convinced and are willing to accept your claim. It is important that any claim you make in your PhD thesis has the support of well-established knowledge, it then becomes easier to accept it by most of the readers. When what you are claiming is a controversial topic, be prepared for inquisitiveness from the reader about, why a certain claim should be accepted? Here comes the role of argument, when you can state to the reader, that you have given substantial reasons to accept the claims. Strong arguments play an important role in your thesis. Thought, there can be more than one type of argument but the objective behind putting up an argument in your thesis is primarily to convince the reader of the claims that have been made by you. Remember that without a solid and substantive argument, the claim is nothing but an assertion. Whatever be the genre of your academic writing, regardless of the merit of the claim you are trying to make it should be preceded by an argument and the claim should be followed by in the conclusion paragraph. In a complex PhD thesis, which most of them are, there can be various layers of argument and hence various conclusions , each one leading to the next argument and then stepwise progressing towards the final conclusion that is the convincing answer to the primary research question of your study.
When writing your thesis, play special attention towards arguing over points and specifying crisply that why they should accepted and contrary claims be rejected gives a lot of weightage to the quality of your thesis and can be a crucial part of being critical. If your thesis lacks depth in arguments, be sure that you would have a dissatisfied examiner who would feel that the quality of your thesis is not up to the mark. In that case, the only support on which your PhD could stand is your verbal ability to argue, else all the effort would go in vain.