I’ve read up on Babson tasks, and they mention that all known tasks are not perfect because there are duals. I’m not sure what this means exactly. What precisely is a “dual” in chess problems?


1 Answer 1


A dual is an alternate solution, other than the intended one, after the first move of a problem or study. If it happens on the first move, the problem or study is called cooked instead.


Ideally, White should have only one move at each juncture that solves a problem. If White has an alternative at any stage other than the first move, this is a dual. A dual is not as serious a flaw as a cook, and in minor lines, duals may be permissible (opinions differ on this point). Some problems make a virtue out of dual avoidance – of two apparently equivalent white moves, only one works.

(source: Wikipedia)

  • Wiki misses a slight point: If Black ignores a threat, this is not seen as a dual...usually. (In olden times, one was less lenient about it.) E.g. Kc8 Rb5 Bg1 - Ka8 Pa7. Black has no defense against Rb8#, so is 1...a5 2.Rxa5 a dual? Mar 17, 2021 at 8:01
  • That may be what the article means by 'minor lines'?
    – Glorfindel
    Mar 17, 2021 at 8:11
  • I'd say the case I describe is a subset of 'minor lines'. I'd define a minor line as anything that is not thematic. A dual minor is still a thing you should strive to avoid nowadays, whereas hardly anyone cares about a dual by ignorance. Mar 17, 2021 at 9:20

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