This thesis looks at two critical urges in Critical Systems Thinking that both complement and critique each other. Firstly, there is an urge to construct in a critical manner. Secondly, there is an urge to be critical about such constructions. They complement and critique each other in the manner in which the second urge requires the first urge in order to understand what it means when one begins to create by construction, and also in which the first urge requires the second in order to understand the privileged position that construction is given in epistemology. These two urges give two stages. Construction relates to four clear conditions that develop from an Architectural study. This study offers two definitions of Architecture : structural longevity and relational modification. Consequently, a Structure and Process are established (first two stages) which together content an Architecture of Critical Systems Thinking (third stage). This Architecture is then applied to Systems Thinking through a study of five Systems Thinkers, this application offers an Architecture as commensurability (fourth stage). The Architecture is thereby offered as author. De-construction relates to four clear conditions that develop from the Architecture of Critical Systems Thinking. Each condition questions the Architectural authority to construct. The Process (reversed to complement and critique) questions the Structural consistency of the Architecture (first). A Structure of Acuity develops that maintains meaning where the Architecture neutralised meaning (second). A Contentless Acuity follows (third), thereby allowing the contentlessness of paradigm (in)commensurability to be discussed as an application of the Acuity of Critical Systems Thinking. The Acuity is thereby offered as reader. To balance these two urges is to read with authority.