Is there a non written rule to which person to use in the PhD thesis, 5 years of using "We" in the papers have brought me to the innate necessity to do it every time I describe something.
Recently, though, one of my lab-mates told me that I should use I, since it is your work, if the thesis were co-written, then it would be a different story.
Is there any standard in your universities, or do you have any preferred practice.
I generally avoid "I" in scientific texts altogether, though some authors are in fact using it if they are the sole author. I can't remember seeing it in a thesis though. In texts with a sole author, I usually understand "we" as meaning the author and the reader, and I'd suggest that it's fine to use it in places where it can have that meaning. For example something like "When substituting a by b, we get ..."
A generally useful advice would be to read into some of the theses written in your group, department, and university (in decreasing relevance), and see whether there is a common pattern.
Summary: Think about the habits and traditions in your field, think about the nature of your field and do not hesitate to take responsibility for your own (possibly not that great) ideas.
Now, let me elaborate more:
The question encourages personal opinions for a good reason. Various sources on writing research papers differ vastly, though it seems majority does not favor the first person "I" form. For one of the more serious in computer science not in favour of "I", see e.g., Knuth's Mathematical Writing (pg.4) - although later on, the material also discusses the opposite (pg.62 and 113).
Now to a personal position. I do make use of "I" in some contexts. Namely, when I write a paper as a single author and I did so in my PhD thesis. At the same time, you should have clear rules when to mix it with "we" and how. For the dissertation, I explained those rules very early on in the preface: I use "I" whenever the text speaks about my own decisions and choices I made and is the default voice. It means, that it's me who is to blame for whatever incorrect decisions exposed in the thesis. Only if I can show that there is an external force which would push anybody on my place to take the same route, I would use "we" to mean the (research) community, or humankind. I use "we", whenever the discourse is explanatory, such as an exposition of a proof. Therein, "we" stands for "me and the reader". I also strictly use "we", whenever I speak about an insight, or a result which was produced in a collaboration, such as developed in a joint research paper with somebody else. As a side-effect, since this voice is not the default one, occurrence of such "we" always enforces a citation to the joint work, which is a Good Thing.
My personal opinion also is that third person is very bad writing style, since it offloads responsibility for the presented results to some external entity. As if it wasn't me who made the stupid decision to push that other guy from the cliff, but the guy was (somehow) pushed from the cliff. In my opinion, "we" solves that problem only a little bit, because now the writer admits a bit of responsibility for the act, but still dilutes it by taking into the game somebody else (either the reader, or the abstract research community). Saying "I did this and that and by doing it I personally found this and that" for me is fully taking responsibility for my results. It's not about bragging, or so. Now in some fields, this might be inappropriate, e.g., in pure mathematics, one studies a problem and is not pushed into any arbitrary decisions (e.g., regarding experimental setup), so a style "we" = "the two of us, you, the reader, and me, the writer" is more appropriate.
It is interesting to see what Charles Darwin did in his scientific writing.
Darwin usually speaks in the first person plural when analyzing empirical evidence he has collected and only uses the first person singular when he is specifically speaking about his own actions, such as, "..many special facts which I have collected," or when he is speaking about his own qualms, such as "I am well aware that there are on, on this view, many cases of difficulty, some of which I am trying to investigate." However, when analyzing his evidence, he always uses "we", such as "we notice", or "we understand"(2). Darwin's change in footing when he is explaining his theory places himself and the reader on the same level and makes him a more "humble" presenter, allowing us to suspend disbelief for at least the time being and trust him.
When Darwin is speaking as the scientist, he uses "we", and when he is speaking as the human being, he uses "I". I really like that distinction.
I find the forced use of "we" when you mean "I" misplaced. It is important to sound as natural as possible in your writing - just look at Richard Feynman. You don't have to use convoluted language to win a Nobel prize. Clarity is king.
The first rule, as usual, is: what is expected of you? Ask your advisor, read earlier theses from your group, etc. to get an idea of what is the established practice.
The advice I give, and which I try to follow myself, is to mix the use of “we” and “I” depending on context. Most of the experimental or simulation work is a team effort, so “we” makes a lot of sense to describe that:
From the results of the simulation, we have calculated the spatial dispersion of ∆, which is presented in Figure 42
However, a PhD thesis should show that the applicant has a clear understanding and autonomy in a given research project, and thus is capable of making technical and strategic decisions (though not always alone, of course). As such, I encourage the use of “I” to describe such decisions, orientations and reflexion. I try to give an example:
After consideration of the points discussed above, I decided to focus my effort for the most part in optimizing the gigawattage of the circuit, which I consider based on all the data gathered to be the factor with the largest potential for improvement.
Silvado gave an answer that is, in my opinion, perfectly applicable to mathematical derivations, and the discussion of results. In those cases, you can safely use “we” to mean “the author and reader”, as in “we thus derive theorem X from lemma Y”, or “we see on Figure 42 a clear correlation between A and B”.
I always view "we" as "you and the reader" and you and your reader journey through the subject together.
I was told that my PhD thesis should be written in the third person. In cases where it was nessacery to reffer to ones-self the term "the author" could be used but use of this term was discoured. The theory goes that the emphasis in acadmic writing should be on what was done rather than who did it.
Personally I dislike this style. IMO it makes it much harder to be clear about what you did verses what is already common knowlage.
My PhD was in Electrical Engineering at the University of Manchester in the UK.
I am a retired professor. I was taught, and I always required, that theses and dissertations be written in 3rd person or, on rare occasions, in 1st person plural. Towards the end of my career, I had students increasingly writing in first person singular. This grated on my nerves enormously. Why? It seemed arrogant and ignored the substantial assistance provided by the committee and the funding agency. Also, it flew in the face of unspoken tradition: that scientists did their work with humility for the betterment of society. Any recognition of the scientist should come later from society at large and the community of scientists.
wemakes us feel so royal . . .