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You might still be in doubt as to whether you really want to do a PhD. Of course, in the end, you are the only one who can decide whether a PhD position would suit you. But before you start applying to positions, consider the following things:
Do you want to continue in academia?
Do you want to pursue an academic career after receiving your doctorate titel, or do you envision yourself in some other professional environment?
If the latter's the case, there might be easier and faster ways to reach your goal. While having a PhD does not necessarily render you overqualified for all jobs outside academia, there is some disagreement over the question whether it gives you any advantage out there in the real world. Of course, this will also depend greatly on the kind of career you envision for yourself, and what your strenghts and weaknesses are. It can be good to realize that
An PhD/academic career isn't for everyone
Being a Research Master student, you have a faint idea about what is involved in doing philosophical research. Still, it's good to take into account the suboptimal work conditions in academia. Research in the humanities is often a very individual activity, and especially writing a dissertation can be a rather lonely affair. If you want to continue in academia, there is the added pressure of having to publish in order to improve your position. Opinions differ on the development of such competition once the tenure track has been started, but it can generally be agreed that the work pressure is high in academia. Luckily, there a lots of ways to deal with these issues, but it is still good to consider whether you're sufficiently stress-resistant to rise to the challenge.
If you are sure you want to continue in academia, a PhD is probably the thing for you. The bad news is:
A PhD does not guarantee an academic career
If you thought that getting a PhD position was hard, the unfortunate truth is that it's even harder to obtain a post doc afterwards, let alone a permanent position. The academic career ladder is often said to be a bottleneck: the higher up you get, the more competitive it becomes. Moreover, in most countries the number of academic positions in the humanities is steadily declining. For some depressing statistics, check out [this information put together by Chris Meyns. Precisely since a PhD offers no guarantee, it is strongly advised not to take out a loan to fund your PhD. As the PhD panel at the Winter School put it: if you cannot get funding for a position, that is a sign you should not do the PhD.
All this may sound bad, but it is mostly to underline that it is important that you:
Have a plan B in place
Major disappointments are unlikely if you actively try to avoid tunnel vision. Sure it's important that, if you do prefer to pursue an academic career, you try everything in your power to strengthen your position and build your CV. But make sure you're not a one-trick horse. Keep developing yourself in other areas and orientate yourself on other possibilities out there so you know you'll make it even if you don't get a PhD or a post-doc position afterwards.
It's all about intrinsic motivation
Knowing all of the above: that a PhD can be lonely and stressful, that it might not help you get a job outside academia, that even inside academia there are no guarantees and that you need to have a plan B, being intrinsically motivated to occupy yourself intensively with some four more years of philosophical research is the most important necessary (some might even say sufficient) condition. On the one hand, a PhD should not be just a means to becoming a professor. On the other, even if you do not necessarily want to end up in academia, you may still decide you are not done with philosophy just yet and really want to get a doctorate. In all cases, the crucial factor is your intrinsic motivation to do philosophy, and importantly: to occupy yourself with the specific topic of your PhD.