Motivation is a type of Act. Person wants (to) Motivation. Arm is part of Person. 
Simple is a synonym of Innocent. Innocent is a synonym of Pure. Pure is similar to Theoretical. 
Act <--IsA-- Motivation <--Desires-- Person <--PartOf-- Arm 
Simple <--Synonym--> Innocent <--Synonym--> Pure <--SimilarTo--> Theoretical 