Is it reasonable to go from ‘x is the current scientific consensus, to the extent one can be detected’ to ‘it is warranted to believe that x is true’?
1. Scientific consensuses change.
The consensus in cosmology was that there was a steady-state universe, then the consensus in cosmology was an expanding universe. Similarly, the consensus in geology was that mountains built up through sedimentation, then the consensus was that mountains built up through interactions of moving tectonic plates. And so on.
The list of scientific consensuses that turned out to be wrong, and which in many cases were replaced by significantly different theories, is long.
(The changes weren’t just refinements of a given view, but often dramatic shifts in how facts were brought together to form a picture of how the universe works or how events transpired.)
We are warranted – through a process of induction – in thinking we have little reason to think we are in some unique period of history now where we have all the answers.
This leads to
2. So, in many cases the current scientific consensus will turn out to be wrong, and often significantly wrong.
The question then is how to determine which case one’s in for a given consensus (relevantly correct, relevantly incorrect?).
There are several signs which suggest a given state of knowledge is incomplete.
a) Is it reasonable to believe that there is a large amount of relevant data that isn’t known yet?
b) Are important aspects of a theory not robustly testable (and tested) yet?
If so, it might be reasonable to think the theory doesn’t capture the terrain exactly right in those areas where it lacks robust testability.
c) Is the area of knowledge rapidly changing?
Obviously, this is a sign that our knowledge of the area is incomplete to some significant degree.
(Theoretical momentum can often lead one astray. For example, you might start explaining things fairly well using a mechanism. It might be tempting to leap to the conclusion that all things can be explained in this way. This is probably an unjustified leap.)
A response might be made that, yes, scientific consensuses are often wrong, and indeed a given one in question may likely be wrong (given considerations like a) to c) ), but nonetheless it is the most reasonable position that can be arrived at to this point.
Is this true? No.
If one has a specific reason to reject a consensus, that reason must be evaluated on its merits. This is because there are ways to know things or considerations that bear on a given theory that may lie outside the scope of the theorists from which the consensus is derived.
Therefore, a consensus can only be a rough guide to what might be the most reasonable position at a given time.