When most people think of cheating, they think of a player planning to do something illegal and actively cheating; i.e., putting extra cards in a sealed deck, manipulating their deck, or purposely drawing extra cards. Unfortunately many players do not realize that it is possible to cheat by not doing something. If the above examples are “crimes” through commission, then there are also crimes of omission, or of cheating by not doing something.
A crime of omission is when you fail to fulfill a responsibility. In Magic, all players in a game have a responsibility to maintain the game state; it is up to every player to ensure that nothing illegal happens. Often both players accidentally fail to do this, and when this happens a judge has to step in to figure out a way to correct the game state if possible and give the appropriate penalties. In situations like these no player is cheating, they are just being careless.
Sometimes one player will make a mistake that results in an incorrect game state and his opponent will make no effort to correct this mistake if it benefits him. Examples of this include: noticing that your opponent has failed to draw a card for the turn and saying nothing about it, allowing your opponent to mistakenly put only one counter on his Umezawa's Jitte after the equipped creature has dealt combat damage, or letting a mistake in calculating a life total go without correcting the error. These are all examples of cheating in a game of Magic.
A common rationalization or argument for this behavior is that Magic is a strategy game and that a player should not have to correct a mistake made by an opponent. While mental ability is a part of Magic the game is really about the choices; what deck archetype are you playing, what card do you cut, what is in your sideboard, how highly do you draft certain cards, etc. You can take advantage of a poor choice an opponent has made. But you can’t take advantage of an illegal play that benefits you.
One thing to keep in mind is that the game does have many non-mandatory effects; those in which the controller of the ability may or may not do something. If your opponent does not draw when a triggered ability that says he “may draw a card” resolves, he is making a poor play and not an illegal action. Again, you can allow your opponent to make poor choices when given a choice.
Once again, this is not about making strategic mistakes or helping your opponent win the game. This is about noticing a problem with the game state and letting it go without calling a judge because the error benefits you. Doing this is cheating, and it will be penalized accordingly.
Chris Richter, Madison, WI