There is a certain group of students who enrol in a Ph.D. programme on a scholarship with an already prescribed topic. The department that assigns them the scholarship, does that with an already prescribed set of objectives they want to achieve in a certain area of research. When the defined topic is there, scholars need to begin the task of further exploration on the topic to understand the gap that their work is going to fill.
The other category of candidates are those who have some idea in their mind on which they wish to work, or they are keen to get associated with a specific scholar. Whatever be the preference, whether the area of study in mind or the desired supervisor, it is the stage to roughly formulate the topic and move on further with the research
After reaching till here, the next stage is to do some assessment of the available literature. It would help you to answer a few questions which are related to the importance, relevance and significance of the study. The more literature you would read, better would be the understanding of the topic, and what is remaining to be explored in the field of study. It is essential that at this stage your supervisor guides you to the most fruitful starting point, to explore the existing content, and review the literature critically.
There are chances, infact in most of the cases, it so happens that the literature review expands your horizons, and gives you a broader perspective and vision to modify your topic in the right direction. When you read, think and further discuss with your supervisor, you can make the required constructive changes in your topic. With multiple rounds of these activities, you topic keeps getting focussed and more specific. Extensive reading is very important at this stage, as this activity is not a one time activity but rather a cyclic action where you have to keep repating the process of reading, thinking, and discussing with the supervisor till the time your expert, and experienced supervisor feels that the proposed sutdy is feasible, realistic, and a the same time sufficient to meet the Ph.D. standards that are required.
Almost all the time, even after the finalisation of the topic, supervisors recommend scholars to undertake pilot study in the beginning stage of the research to ensure that the topic is going to finally culminate into a fruitful research.