I once had a discussion about this topic with a colleague. >For instance, in a technical field it can often be very difficult to understand much less evaluate

I once had a discussion about this topic with a colleague. >For instance, in a technical field it can often be very difficult to understand much less evaluate a fully reasoned argument. I think at the time I had fluffed a response to the question this answers which is "well how do I know that xyz guy really knows his stuff and isn't just a so-called-expert in his field, why should I believe him?". But this sums it up nicely, it can take decades to learn enough about a field to understand the arguments properly.