The title of this post is a question one of our undergraduates asked, and which all members of staff were asked to answer. I wrote up my answer today, and thought it would be worth sharing why I think this is the wrong question to ask. (The answer below is written to my fellow colleagues who were asked to answer this question, not to the student who originally asked it.)
I do not think that this question is properly formed. Philosophy is not a discipline of authors and their works but of techniques and concepts and ideas. Putting the emphasis on books and philosophers misses the point, in my opinion, because it is predicated on the idea that our goal in an undergraduate philosophy programme is to teach students philosophy.
"But of course that's what we're supposed to be doing!" you reply. I'm not so sure it's so obvious, and I'll counter with a different proposal for what we should be doing, instead of teaching them philosophy: We should be teaching them how to be philosophers.
Equipping a student to be a philosopher is equipping them with a variety of philosophical tools stemming from different philosophical traditions:
- The ability to write clearly and precisely.
- The ability to read a complex article and understand it.
- The ability to draw distinctions and reason from definitions.
- The ability to recognise and create counterexamples.
- The ability to ask appropriate questions.
- An understanding of how we know things and what counts as evidence.
- An understanding of what exists.
- An understanding of what we ought to do.
- An understanding of praise and blame.
- (And other things; this list is not complete.)
How we get students to the point where we have all of these doesn't matter; we can do it with any texts and any authors that suit the purposes. Focusing on "required" or "canonical" books and authors reduces philosophy to a set of principles, a set of truths, a set of facts. In my opinion, this misses entirely the point of studying philosophy! Now, if you put concepts and techniques first, then it's likely that certain texts will fall out as "canonical", since certain texts are the first/clearest place in which a specific concept or technique is presented. But often the first place something is articulated is not the best place in which to introduce a student to the subject -- for example, I think students should know about the syllogism, propositional logic, and predicate logic. But I wouldn't advocate teaching any of these via Aristotle, the Stoics, or Frege (at least not as the primary texts!)
I've written more on the difference between teaching philosophy vs. teaching how to be a philosopher (since writing that post, my views have become rather more radical, in that I think the balance should be skewed much more towards teaching them how to be philosophers, even if this means that they end up with "gaps" in their education, e.g., because they haven't read Aristotle, or Descartes, or Russell. Also relevant to this discussion is why I think it is so crucial that we teach logic to our first year students, especially if our goal is to train them to be philosophers.