When to write the introduction (academic writing)

An open letter to PhDs:

Several of you looked unhappy when I said in our meeting last week that the introduction is the last thing you write, to make sure it sets up and matches the conclusion.  I want to be clear about this.  You should be completely honest about what you actually did.  But a dissertation is not just a history of what you did and why in the order you did it.  It is first and foremost an effective communication of what you learned.  The introduction is there to make the dissertation easier to read, and to help the reader decide whether to read it.  It is not there to recount a history.  It's possible that there will be no point in your dissertation where you record a chronology of what you did in order.  There may be entire projects you did during your three years here that aren't mentioned in your dissertation.

A dissertation consists of a thesis and an account of evidence that supports it.  So far as that evidence results from your own experiments rather than things you've read, you should of course say what you did and why you did it and how it went.  But even then, it's possible that *when* you did it may never enter in.

I'm not sure whether that's why you looked perturbed.  Maybe you think for some other reason that you will know in advance what you are going to write.  That's not how writing works, not even for a paper, let alone a dissertation.  The process of writing is not just a transcribing of your fully formed thoughts.  Writing is always a synthesis, and even a good article (let alone a dissertation) has more in it by the end than you fully knew when you started to write.  Writing offers a chance to check details in the literature and to examine your own arguments carefully. That's how writing goes, and that's why you write the conclusion and introduction last, even though they frame the entire dissertation and are the only parts many people will ever read.

In fact, it's because they are the only thing most people read that they are the last thing you write --- the thing you write when you know the most.

More advice on being a PhD student is on my dissertations page.