You should've just told me that 6 is not compatible with 5, so that specifying an explicit version number won't cut it (I checked how version checking works and that does seem to be the case). You can still use `REQUIRED` instead of your check, though.

> So, my question was (I forgot the question mark), how do tell cmake to choose the newest version of vtk if it 'finds' two?

Here's what the documentation says:

> When multiple package configuration files are available whose version files claim compatibility with the version requested it is unspecified which one is chosen.  No attempt is made to choose a highest or closest version number.

So I don't think that's possible.