The central "don't do that," at the heart of the GUMSHOE system concerns the mechanism whereby players in an investigative scenario gain the clues they need to solve the mystery. The tactical tradition treats this as a skill use like any other, with a chance of failure corresponding to your investment of character resources into that skill. Say you need to find out what your suspect's grandfather was doing during World War II. You roll your Library Use skill. If you allocated enough points to Library Use during character creation and/or manage to score a lucky roll, you get the information you need. If you invested lightly in the skill, or roll poorly, you're screwed. In theory, that is.
In reality, GMs either fudge the roll, or improvise a workaround, giving the characters repeated shots at discovering the same fact with various abilities, until one of them finally succeeds, permitting the plot to free itself from its rut and lurch onward. The standard approach borrows some of the outward aspects of a tactical game, but in fact relies on GM kludging to prevent them from operating-as it must, to serve the demands of story structure, which craves ongoing forward momentum.
GUMSHOE says, "Don't do that." Since the end of the process is a foregone conclusion-the characters get the info they need-why waste time, focus and creativity with a system that provides only the illusion of chance? Instead ,GUMSHOE provides a character generation system which guarantees that someone in the group will have made the necessary investment in every information-gathering ability, and which then grants access to clues on that basis. It is a simpler, streamlined way of achieving what good GMs are already doing-without the pointless and annoying faffing about.
