Hi Bronin, I realise this message is a few months late but I stumbled across your post. I am currently in the process of submitting my doctoral thesis and thought you might like a few tips on choosing a topic for your thesis. I started my thesis a year after finishing my Master's degree and I have been studying it now for four years. Looking back on the decisions I made in this time, I do not regret choosing to pursue it and I have managed to contribute novel work to the field but I do believe I could have picked a topic better suited to me. My main piece of advice for choosing a topic would be: What questions do you personally want to answer that no-one else is working on currently? It took me the first two years of my PhD before I came up with the research questions and methodology I wished to pursue. Read, read and read. In a standard PhD you will spend the first 6 months to a year reading around 200-300 papers. As you are not pushed for time, you could spend years reading. I have personally found that Books provide much more information than papers, particularly if you're not an expert in the field. Then use papers to help expand and push your learning to the boundaries of science and to select your topic, though be critical of what you read. I wish I'd found this Ioannis' article (2005) in my first year (Doi:10.1371/journal.pmed.0020124). To have the biggest impact, try to quantify the most important elements and the limiting factors in your subject and strive to improve them, with an eye to being able to develop a methodology that is simple and that can deliver with certainty. I hope this helps and I wish you the very best!