+
+
+ (iii.2) γ = γ <=< (unit G)
+ when γ is a natural transformation from G to some MR'G
+ ==>
+ unit <=< γ becomes: ((join R'G) (M γ) unit)
+
+ substituting in (iii.2), we get:
+ γ = ((join R'G) (M γ) (unit G))
+
+ which by lemma 2, yields:
+ γ = ((join R'G) ((unit MR'G) γ)
+
+ which will be true for all γ just in case:
+ ((join R'G) (unit MR'G)) = the identity transformation, for any R'G
+
+ which will in turn be true just in case: