Situate your research in the broader a context
The main purpose of a literature review is to situate your research in a broader context.
No academic research exists in a vacuum. Most often, new academic research builds upon old academic research. By reviewing the state of the art, and what existing studies have found, you are able to better understand how your research can build upon it.
It’s important to remember the key purpose of your PhD: to make an original contribution to knowledge of publishable quality. To be able to make an original contribution to knowledge, you need to first tell the reader what knowledge we already have in a particular field, and what gaps exist within it. That is where the literature review comes in.
It’s in the literature review that you highlight the gap that your thesis will then fill. Or, in other words, where you state what contribution your thesis will make.
To highlight the gap in the literature and therefore situate your contribution, you need to first discuss the current state of the art in your niche.
That requires a huge amount of work. By definition, to make the case that a particular gap exists, you need to present a comprehensive picture of what currently exists in order to then highlight what’s missing.
Seen in this way, the literature review is there to set the stage for your own study. It’s there to say ‘here’s everything we already know, and here’s what we don’t know’. It’s your job in the literature review to convince the reader that the gap you talk about is actually there and that it is a worthwhile endeavour to actually fill it.
If you do those convincingly, your ‘original contribution’ is built on safe ground. If you do it poorly, you may not make a convincing enough case that your contribution is either original or worthwhile.
Make the case for your research
Another job of the literature review is to make the case for your research. It’s there to problematise the existing literature in order to highlight a gap that your research will then aim to fill, driven by your research questions and research aims and objectives.
Your job is to tell the reader what’s wrong with the existing understanding of your topic. It may be that there are methodological flaws, or that there are gaps in our empirical understanding. Or, it may be that the particular perspective or approach taken is somehow problematic. Whatever it is, your job in the chapter is to articulate that problem and then situate your research question as your path to fixing it.
You can think of a person developing a new type of mobile phone. In order to be able to do so, they need to have a good understanding of how old mobile phones are made, principally to understand what problems there are with those existing designs and to see where things can be built upon and improved. Your PhD is the same.
To be able to make an original contribution to knowledge in your field you need to know what it is that your field is discussing and, crucially, what problems there are with those discussions.
Educating you in your discipline
Beyond making the case for your research, the literature review is also there to make you a better academic. The process of conducting your literature review will educate you thoroughly in your discipline, and give you a rounded understanding of the major debates, theories, concepts and findings.
You’ll need to demonstrate to your examiner that you have a comprehensive understanding of your discipline and that you understand the major debates, seminal texts, key findings, major theories, and so on. The literature review is your opportunity to do that.