(Rather than the common term "cold fusion" I will use the term "solid state fusion" since "cold fusion"
was meant to refer to muon catalyzed reactions.) We should not believe in solid state fusion because it requires at least THREE "miracles." First, the extremely good confinement of the fusioning nuclei in the solid state media.
Second, the large production of energy with very much reduced production of radiation (neutrons, gammas, etc.). Third, the fusion reaction in light hydrogen (not just heavy hydrogen). Any one of these is a near "miracle" and has a very low probability of occurrence. The possibility of solid state fusion being true is then the product of these three! We should not believe it without extraordinary evidence. (i.e., something well beyond the evidence we expect for normal scientific claims.)