How to argue like a philosopher

This is a summary of a workshop on argument reconstruction that I gave to some fellow PhD students at the MRC/CSO Social and Public Health Sciences Unit at the University of Glasgow in 2021. This is an only slightly expanded version of the slides, and is mostly here for the benefit of the people who attended at the time.

I can deliver this as a 90- or 120-minute remote workshop, including some practical exercises and group discussions – email me if you’re interested!

What is an argument?

In everyday language we use the word “argument” in a lot of different ways, but to a philosopher it means something very specific. Let’s go through some dictionary definitions (from just to be clear about what it doesn’t mean.

What we’re talking about is a combination of the two with ticks: something that’s intended to persuade the reader or listener of something, by using a process of reasoning.

(The last one is kind of semi-right. But actually a lot of the time when we use the word like this, we really mean more like what philosophers call a “premise”.)

What is an argument?

An example:

Statement by statement:

Formal definition of an argument (Bowell et al):

The “standard form”

In standard form:

“Reconstructing an argument” means identifying the premises and conclusion in an argument, and rewriting it in the standard form.

Why bother with reconstructing arguments?

Good and bad arguments

Here are two pretty unconvincing arguments:


These are both unconvincing, but they seem unconvincing in very different ways.

Validity and soundness

We use the terms validity and soundness to distinguish between two different characteristics that can make an argument persuasive or unpersuasive.

Saying that an argument is valid means that:

Or equivalently:

Saying that an argument is sound means that:

Implicit premises

Sometimes people don’t explicitly spell out every single premise in an argument. In that case we need to figure out what’s been left unsaid, and state it explicitly in our reconstruction.

This is not a valid argument. But if someone were to say something like this, they probably have something like the following P3 in the back of their minds:

Adding in implicit premises like this is helpful, because it makes it clear what assumptions you need to make for the argument to work. Often the premise that’s left unsaid is the most controversial or questionable one. This reconstruction makes it clear that it’s a pretty extreme position, and it would take some effort to justify, because P3 is a very strong claim.

The principle of charity

From Bowell et al: “Argument-reconstruction is essentially a task of interpretation. What we are trying to reconstruct, to represent as clearly as we can, is a certain train of thought, of reasoning – however well or badly the arguer may have succeeded in expressing it.”

Even if your ultimate aim is to show that an argument is wrong, your reconstruction should give it the best possible chance of succeeding.

If you reconstruct your opponent’s argument to make it look weak, it’s easy for them to say “oh, but that’s clearly not what I meant” (plus you’ll seem like a bit of a jerk).

Intermediate conclusions

One of the premises in an argument could itself be the conclusion of another argument.

Argument reconstruction step by step

  1. Identify the conclusion
  2. Identify any explicitly stated premises
  3. Try to write them down in the standard form (P1, P2, …, C), and assess whether the result is valid
  4. Identify any implicit (unstated) premises needed to make the argument valid, and add them in (if at all possible)

Some additional questions to think about:

An aside: inductive arguments

An example:

This isn’t valid, strictly speaking, but it does seem to tell us something useful about whether we should believe the conclusion. How can we make sense of this?


We’re now ready for some practical exercises.

The photo below is of Ronald Fisher, probably one of the most famous statisticians in the history of statistics. The examples I picked out are all from the literature about smoking and lung cancer from the 1950s, and one of them is from Fisher. He was an avid smoker, and extremely critical – often in pretty arrogant terms – about the idea that smoking might cause lung cancer for his entire life. In retrospect, his articles can be kind of entertaining to read, now that we know that he was completely wrong.

The statistician Ronald Fisher smoking a pipe

Why does this matter?

Write more clearly

Think more clearly

Be the change you want to see in the world