While arguing from silence is a logical fallacy, I think there are times that an argument from silence must be reckoned with.  For example, in discussing whether Matthew 28:19 originally read “in the name of the Father, Son, and Holy Spirit” or “in my name,” some Trinitarian scholars argue that the latter is original.  “In my name” does not appear in any extant manuscript, so what is there basis?  One reason is Justin Martyr’s silence on the passage.  In one of Justin’s work he was arguing for “Father, Son, and Holy Spirit” as the appropriate baptismal formula, and yet he never once appealed to Matthew 28:19 for support as we would expect for him to have done if Matthew 28:19 originally read “Father, Son, and Holy Spirit.”  Since he did not, it stands to reason that Matthew 28:19 did not read “Father, Son, and Holy Spirit,” in Justin’s day (or at least in the manuscripts he had access to), but rather “in my name.”  While this is an argument from silence, it is a strong argument nonetheless.