Evidence in support of a claim

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Toulmin (cited in Hart,1998; Wright, 2012) developed a model of an argument that I find really helpful in thinking about what is important when I am trying to argue a point or convince someone about something.  (if this is new to you I’d highly recommend the youtube video in the reference list – Wright, 2012).

Whilst there are lots of different elements in the model, the key idea is that if you are to make a claim, then you should provide appropriate evidence to support that claim.  The other day, I was in a conversation which made me realise that ‘appropriate evidence’ can be quite a contested term – it means different things to different practice communities. But, as I reflected on the conversation, I also realised that it means different things to me in connection with different types of claim.  So if someone claimed “Paracetemol is good for headaches” I would expect different sort of evidence to a claim like “This man committed murder” and that would be different again to the sort of evidence I would expect for a claim such as “SWOT analysis is the best tool for making strategy”.  I also realised that what may be good enough evidence for me, may not be good enough evidence for someone else – so in a circular way, the idea that the evidence is sufficient to support a claim is itself a claim!  Whether the claim is good enough arises in a social dynamic – it’s in the eye of the beholder.

This then raises the question as to where good enough ‘evidence’ comes from.  In some cases – particularly claims about the effectiveness of a drug – I’d expect evidence to come from rigorously conducted research i.e. that it is “scientific evidence”.  Here there is a clear hierarchy of evidence as discussed by this helpful blog from Logic of science (2016)

But what if the evidence isn’t ‘scientific’ in that sense – where the type of claim is not conducive to being supported by research studies?  What else can we draw on to support a claim?

Sometimes, referencing the work of others is a good way of evidencing a claim – this is a form of ‘expert opinion’.  In essence this means we are building an argument on the argument that someone else has already made.  If the other person is understood as an authority on the issue and has argued their claim well – then it is perfectly okay to rest on their claims as evidence for our own plausible argument.  The risk is where that ‘expert opinion’ is a little dubious – for example it is only published in non-peer reviewed sources like blogs(!), social media and so on – the key thing is if we are to rest our argument on the claims of others, we do need to be discerning in the way we rely on those claims and consider their credibility.

We also use evidence from our own experience to support our claims.  This is trickier again – it raises questions about the difference between anecdote and ‘good’ use of experience, it challenges us to think about the role of our emotions, interpretations, and our own actions and interactions in “producing” that evidence.  As I discovered when I wrote this blog, it can also be difficult to write our experiences in a way that is specific enough to support a claim.  There is a big difference between drawing generically on years of experience in an industry (e.g. as an engineer…) to a very specific experience within a long career.

I have all sorts of connected ideas going around in my head so it’s tempting to just leave this blog unfinished for now – but in my new spirit of writing more often, I am going to publish.


Hart, C. (1998) Doing a literature review: releasing the social science research imagination, Sage/Open University, London

Wright, D. (2012) ‘The Toulmin Model of Argument: A writing tutorial’, YouTube. Available at https://youtu.be/D-YPPQztuOY [Accessed 13 Dec 2018]

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