From assurance to ignorance in one easy move – a classic piece of equivocation

Equivocation is a logical fallacy where the same term is used in two different ways within the same argument. For example:
A candle is brighter than nothing
Nothing is brighter than the sun.

Therefore,
A candle is brighter than the sun.

Spot the problem here? ‘nothing’ in the first premise means nothing in the sense of absence of light. In the second premise, ‘nothing’ means ‘no thing’, ie, there is no thing brighter than the sun. In this case, the absurdity of the conclusion sets alarm bells ringing. But equivocation happens all the time, and can often be harder to detect.

I heard a good example on Radio 4 last week.

The Today Programme was reporting on research which suggested that obesity could reach crisis levels within a few decades. In the spirit of ‘something must be done’ the programme was canvassing experts as to how to combat obesity — better advice, labelling, perhaps even controls on fatty foods?

At this point, a spokesperson for food manufacturers was brought in to fight their corner. As you might imagine, he was sceptical of restrictions on foods.

The presenter asked Jones ‘why not bring in a tax on fatty processed foods? That might change people’s behaviour.’

The spokesperson’s response was robust — ‘All the evidence suggests that levying a tax on foods does nothing to change people’s behaviour.’

This was quite a strong claim, and the presenter picked up on it. ‘Can you tell us more about this evidence?’

The spokesperson responded — ‘Ahem, I’ve not seen any evidence that shows that tax on food leads to a change in behaviour’.

I laughed out loud at such a blatant equivocation. But the presenter moved on without challenging the spokesperson.

Can you see the problem with changing from ‘all the evidence suggests this is a bad idea…’ to ‘I’ve not seen any evidence which suggest this is a good idea…’? There is a not-so-subtle shift from assurance (‘all the evidence’) to ignorance (‘I’ve not seen any evidence’). Perhaps this is such a frequent move for those on the spot in the media that it would be tedious to challenge it.

Watch out for equivocation folks. It will, as Hume might put it ‘involve you in absurdities’.

PS – in equivocating to his ‘I’ve seen no evidence’ claim, our spokesperson commits a further fallacy, that of ‘argumentum ad ignorantiam’. This involves equating lack of evidence with a decisive proof against a claim. Not the same thing!