An appeal to nature is an argument that says a thing is good "because" it is 'natural', or bad "because" it is 'unnatural'. It can be a bad argument for two reasons. First, not everyone agrees on what is "natural" or "unnatural". For example, eating meat is natural to some people and unnatural to others. Second, even if something is clearly natural or unnatural, that alone does not mean that the thing is good or bad. For example, many "natural" plants and animals are poisonous, but unnatural things like medicine and vaccines can be helpful against diseases. 