Jacob warned about those who sought for that which they could not understand (see Jacob 4:14). Their zest for exploring and speculating is not matched by their enthusiasm for obeying and doing. Consequently, such individuals do not really come to know for themselves (see Alma 5:45-47). Without that personal witness they are ambivalent and unable to defend gospel truths or doctrines. It is people's incapacity to defend the faith, wrote George MacDonald, which can turn them into persecutors.