Oblique Strategies (subtitled over one hundred worthwhile dilemmas) is a set of published cards created by Brian Eno and Peter Schmidt first published in 1975, and now in its fifth edition. Each card contains a phrase or cryptic remark which can be used to break a deadlock or dilemma situation.

Examples:

• State the problem in words as clearly as possible
• Only one element of each kind
• What would your closest friend do?
• What to increase? What to reduce?
• Are there sections? Consider transitions
• Try faking it!
• Honour thy error as a hidden intention

From the introduction to the 2001 edition:

These cards evolved from separate observations of the principles underlying what we were doing. Sometimes they were recognised in retrospect (intellect catching up with intuition), sometimes they were identified as they were happening, sometimes they were formulated.

They can be used as a pack, or by drawing a single card from the shuffled pack when a dilemma occurs in a working situation. In this case the card is trusted even if its appropriateness is quite unclear...