"What is Thinking?" explores the multifaceted nature of thought, examining its basic mechanisms as information processing and neural activity, while also considering philosophical and psychological perspectives. It identifies various types of thinking, such as analytical, creative, and critical, highlighting their diverse functions. The text also discusses the dual nature of thinking, acknowledging its power as a tool for problem-solving alongside its potential pitfalls like overthinking and cognitive biases. Ultimately, the source grapples with the profound question of the thinker's identity, presenting ideas ranging from the self as an illusion to a deeper consciousness or a self-referential loop.