In my opinion, if you are a PhD student and is working on developing and proposing a thesis, there are at least 5 strategies to support your thesis so you are as the researcher will really believe about the ‘truth’ of your thesis, and convince your reviewers and your readers.
1. Show that you have learned and read or have knowledge many about the related literature! (usually presented in Literature Review chapter)
2. Explain from Logical point of view! If we use logical or derivation approach, explain your deductive or inductive analysis!
3. Justify by previous related studies! Quote the findings or the prominent authors argumentations.
4. Support by empirical data! (could be obtained by survey, interview, primary or secondary data, etc)
5. and last but not least, support by publications, especially highly rank journal/conference!