Abstract : The fragmentation of human performance theory across discrete psychological disciplines has produced a significant diagnostic gap in applied organisational psychology. Foundational frameworks in motivation, cognition, and behavioural science each explain isolated dimensions of human functioning, yet no integrated model maps the interdependent pathways through which these dimensions collectively generate or undermine synergy in professional settings. This paper introduces the Pragadian Model of Human Synergy (PMHS), an original theoretical framework developed through a Theoretical Integration Review methodology and validated against six selected historical cases. The PMHS maps human functioning across four interdependent states: Humanistic, Cognitive, Motivational, and Behavioral. The research proposes that synergy is produced not by the strength of any single state but by the quality of signal transmission between all four, a principle termed Synaptic Coherence. The Upstream Priority Principle establishes the Humanistic State as the foundational anchor of the system. The Synergistic Amplification Effect explains the non-linear dynamics through which small upstream improvements generate disproportionate downstream gains. The Masked Effect identifies a critical condition in which Behavioral output appears healthy while upstream states are collapsing silently, creating false synergy that precedes catastrophic organisational failure. Six formal theoretical propositions are advanced and validated across cases including Google Project Aristotle, Apollo 13, the All Blacks rugby programme, the Challenger disaster, the Enron collapse, and the Deepwater Horizon catastrophe. The paper argues that the PMHS addresses a persistent connectivity gap in organisational psychology and provides a structured theoretical architecture for future empirical validation and practical application.