There are five possible uses of Logic Skill:

• May be used to augment an Investigation Skill at the end of a research project (e.g. find out some information about a xenos, find information on someone in the Imperium’s far past, locate information on a forbidden planet, etc.). May reduce the time taken for the research.
• May be used as an Investigation Skill in cracking a cipher. (IH pg227)
• Once per session, may make a Very Hard Logic Test to experience an epiphany in the form of a conjured idea from the depths of your mind regarding a conundrum being faced.
• Much like the Incantation Talent for the psyker; may be used to recall the mathematical formulaes, correct rituals and mechanical incantations to augment a Tech-Use Test on a machine. Alternatively, may be used to assist another Acolyte’s Tech-Use Skill Test.
• May be used to try to soothe angry machine-spirits. Permits a Difficult Logic Test to coax the machine-spirit into behaving itself.