body: [*O'Sullivan & Hilliard's The Law of Contract*](https://www.amazon.co.uk/OSullivan-Hilliards-Law-Contract-Janet/dp/0198807821/ref=dp_ob_title_bk) (2018 8 ed). p. 312.
  
  
  
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  The green (party's believing a mistaken unreasonable belief) obviously can be distinguished from the red (about causation). Furthermore, I don't think the HCA Justices in [*McRae*](https://en.wikipedia.org/wiki/McRae_v_Commonwealth_Disposals_Commission) would be dumb enough to concoct two limbs that couldn't be distinguished.
  
  
  Thus how can the orange contend that the green "is identical" to the purple, but that the purple makes unnecessary the red? With math symbols, if green ≠ red and green = purple, then how can purple make unnecessary red? 
  
  
  
title: How does the first limb of the McRae test make the second limb unnecessary?