This is an individual chapter of Theory of Constraints Handbook. This chapter provides an overview of the Thinking Processes, their nature and use; addressing the TPâs conceptual, philosophical and methodological foundations; cataloguing their use and practice as reported in the published literature; discussing the need, the design and purpose of the TPâs; and reviewing their effectiveness, on their own, in concert with one another, or with other decision-making methods. We find that TOC serves as a near-complete methodological set on its own, and note synergies through multi-methodological use. We identify and discuss issues raised in the literature: the need to gain further recognition from professional groups and academia, and gaps such as longitudinal and empirical studies. We suggest forging links with cognate fields and disciplines to build further acceptance for TOC.