Excessive testimony: When less is more

This paper identifies two distinct dimensions of what might be called testimonial strength: first, in the case of testimony from more than one speaker, testimony can be said to be stronger to the extent that a greater proportion of the speakers give identical testimony; second, in both single-speaker and multi-speaker testimony, testimony can be said to the stronger to the extent that each speaker expresses greater conviction in the relevant proposition. These two notions of testimonial strength have received scant attention in the philosophical literature so far, presumably because it has been thought that whatever lessons we learn from thinking about testimony as a binary phenomenon will apply mutatis mutandis to varying strengths of testimony. This paper shows that this will not work for either of the two aforementioned dimensions of testimonial strength, roughly because less testimony can provide more justification in a way that can only be explained by appealing to the (non-binary) strength of the testimony itself. The paper also argues that this result undermines some influential versions of non-reductionism about testimonial justification.