Deliberation is not a black box. In this paper, we look at intrapersonal deliberation, a process different from interpersonal deliberation. In particular, we examine two variables, i.e. knowledge access and reflection, looking at their effects on attitudes, attitude certainty, and willingness to express opinions. A between-subjects 2×2 factorial experimental study (N = 83) shows that both knowledge access and reflection could serve as 'double-edged swords' in deliberation. Knowledge access changed attitudes towards a milder position while reduced willingness to express opinions in public. Meanwhile, reflection increased perceived attitude correctness, which might have a mixed implication for deliberation. Further theoretical and practical implications are discussed.