Question: if you want to falsify a theory, do you need a plausible alternative theory?
Toy-examples of falsification suggest not, but I think they mislead. For example: my theory is “there is a fairy in my cupboard”. Potentially falsificatory test of this theory: open cupboard – is there a fairy there? Ignoring for the moment the problem of the impossibility of hard falsification, it looks fairly straight forward. That was the theory, there was the test.
However, this toy example is so simple it allows us to leave implicit the plausible alternative, namely there is no fairy in the cupboard. If no plausible alternative is to hand, I don’t think identifying a potentially falsifying test is so straightforward.
I arrived at this train of thought via a discussion last night about vegetarianism. I was trying to convince people that we have have an evolved disposition to obsess about and ritualise our food behaviours, so that any food habit, however arbitrary or initially unideologically – for example not eating meat just because you happen to live with vegetarians – can quickly and easily embed itself in our psychological preferences and become the subject of purity rituals and taboos (“Don’t cook my vegeburger in your bacon fat!” sort of thing).
I’ve been trying to think of a way to test/falsify this theory and can’t. This either means that the information content of the theory is actually minimal – i.e. it isn’t actually saying anything – or it means (my best guess for the truth) that my scientific imagination isn’t very good. And I think the missing link in my chain of thought it the lack of any apparent plausible alternative. Simple negating the theory (“food behaviours are not subject to purity obsessive behaviour”) doesn’t produce an interesting theory, and the tests that it suggests would, i feel, be passed without actually providing evidence that my theory is any good at all, just better than nothing. In other words, I think I would find people are obsessive about food behaviours, some of which are pretty arbitrary, but I don’t think this would allow me to convince anyone that what I am saying is true.
The problem may be with the nature of the theory (an evolutionary ‘just so’ story?) rather than with falsficiation.