Media coverage of G20 protests this weekend was awash with the words ‘violence’ and ‘violent’. Protests ‘turned’ violent, police tried to ‘contain’ violence, public figures speak out ‘against’ violence. So what is violence?

In particular, what do people mean when they use the word in statements like this: “I respect people’s right to protest, as long as they do it non-violently”, or “Political disagreement is one thing, but violence is unacceptable from any quarter”, or this statement from Toronto’s mayor: “they’re not protesters…they’re criminals who came to Toronto…and deliberately committed violent acts”.

Violence, we’re led to understand, is a very bad thing, and is moreover qualitatively outside the space of reasonable political debate and protest. If this is the case, we should expect that defining and identifying violence should be pretty easy and straightforward.

If you go to google for definitions, though, you swiftly find yourself in a circle: ‘violence’ means “an act of aggression”, and ‘aggression’ means “violent action that is hostile”. Or “violence is the expression of physical or verbal force against self or other”…but ‘force’ has among its meanings “a powerful effect or influence”, “physical energy or intensity”, or…”violence”. But that’s standard – if it weren’t, dictionaries would have put a lot of philosophers out of a job.

But surely we know, in practice, which acts are violent and which aren’t, right? Well, for some core cases, sure. We can recognise murderous assaults, wrestlings to the floor and carryings away, punches and kicks, shootings and stabbings, etc. as violent acts. But then things begin to get much trickier.

For instance, is any unwanted physical contact violent, even if it’s gentle? Certainly it might be experienced as a ‘violation’. What about to a sleeping person – stroking a cat or a child in its sleep seems like the opposite of violence, but performing sexual acts on someone who’s asleep (including children, and maybe cats?) would, under many circumstances, be a form of sexual violence.

Guns prove that skin-skin contact isn’t needed for things to count as violence, and cases like poisoning, or setting fire to a building with people inside, suggest that violence need not be instantaneous in its effects. But then if it is violence to poison someone, isn’t it also violent to poison a whole population’s air and water – even a little bit? I’m about to get on a plane (so apologies if this post is rushed): am I behaving violently?

I won’t try to resolve all of these edge cases, because they still all have one thing in common: they are all actions that physically affect the body of some animal. But the use of the term ‘violent’ for the G20 black-bloc indicates that acts can be regarded as violent without doing this. Breaking a window is also described as violence – “violence against property”. But roadworks, or removing an old window to put in a new one, are not seen as violence. Does the difference purely consist in who has legal ownership? Or would the black-bloc not be called violent if they had done something constructive with the windows – perhaps made a big piece of street-art out of broken glass?

Then there’s things like verbal violence, or emotional violence. How does this differ from disliked words, or things that make someone feel bad? What about loud noises or overcrowding? And then ‘symbolic violence’, which is an even trickier concept to get a handle on.

Anyway, that’s probably enough to set up the question. I won’t try for a complete answer right now, but I’ll make a few comments.

We’re torn in two different directions here. For the concept of ‘violence’ to be useful, especially for the sort of use we saw it being put to above (“I accept political protest, but only as long as it refrains from violence”), it has to be relatively narrow. We already have the category of ‘bad things’, or even ‘very bad things’. The concept of ‘violence’ is only analytically useful if it can pick out a specific sub-set of things which are bad.

Moreover, one of the key uses of ‘violence’ is to distinguish a ‘political’ space in which disagreement is tolerated, from a ‘sub-political’ space in which violence occurs. Non-violence is the precondition for political dialogue. This requires that whatever ‘violence’ is, it be something that can be identified in a relatively simple, objective way, i.e. without assuming one contentious political position. If abandoning violence is what enables dialogue, then you should be able to distinguish violence from non-violence before you start the political dialogue.

But on the other hand, when we start considering all the things that people might describe as ‘violence’, we find ourselves drawn in the opposite direction. If flying in a plane can be violent, or if words can be violent, or if redecorating a street can be violent, then it looks less and less likely that we’ll be able to distinguish violence from non-violence prior to engaging in political dialogue.

It begins to feel like the concept is stretching beyond recognition, as if ‘violent’ is becoming less and less distinct from simply ‘bad’. And this is worrying, because even though I may disagree with the particular ways that discourses on violence operate at the moment, I think the idea of non-violence as a precondition for political dialogue is a very valuable idea and I don’t want to just give it up.

I think it’s necessary to understand ‘violence’ first of all in psychological terms, in terms of what’s involved in experiencing an event as violent, and then to build up from that, trying to say which perceptions of ‘violence’ should be accepted by others and which shouldn’t – not assuming that there is a pre-existing objective truth about what is violent, but hoping that there can be more and less rational ways to proceed towards intersubjective agreement.