In a critical thinking textbook I’m trying to study from, there is an exercise which gives groups of three different independent reasons from which I must select the one which supports a stated conclusion.
Conclusion: Blood donors should be paid for giving blood.
(a) The blood donor service is expensive to administer.
(b) People who give blood usually do so because they want to help others.
(c) There is a shortage of blood donors, and payment would encourage more people to become donors.
(Anne Thomson, <i>Critical Reasoning - a practical introduction</i>.)
For each question I must pick the answer which could be a reason for a conclusion, say why it is the right answer, and why the other options are wrong. I’ve had absolutely no problems selecting the correct answer, but I can’t seem to say why. It would seem that I could easily say THAT a particular reason gives or doesn’t give support to a conclusion, but I can’t seem to put into words HOW or WHY.
So my question is, why and how do reasons support conclusions? Or what does ‘support’ or ‘gives us reason to believe’ mean? Or why and how do conclusions 'follow' from reasons?