Newport defines deep work as professional activity performed in a state of distraction-free concentration that pushes cognitive capabilities to their limit. It is the book's protagonist — not a person but a practice that Newport argues produces the most valuable output, the greatest skill development, and the deepest sense of professional meaning.

Non-cognitively demanding, logistical-style tasks often performed while distracted. Shallow work is the book's antagonist — not evil but insidious, filling available time through organizational default and cultural pressure while crowding out the deep work that produces genuine value.

Jung's construction of the Bollingen Tower — a stone retreat in the woods where he did his deepest thinking — serves as Newport's archetypal example of creating physical and psychological architecture for deep work. Jung maintained an active clinical practice and social life in Zurich while reserving the Tower for concentrated intellectual work, embodying the bimodal depth philosophy.

Newport positions himself not just as an observer but as a practitioner of deep work — a computer science professor who publishes at an elite rate, writes bestselling books, and stops working at 5:30 PM every day. His personal practice is integral to the book's persuasive power, serving as a lived proof of concept.

Drawn from Sophie Leroy's research, attention residue is the phenomenon where switching between tasks leaves cognitive residue from the previous task, degrading performance on the current one. This concept provides the scientific mechanism for why multitasking and constant email-checking reduce output quality.

Newport's proposed method for evaluating digital tools — assessing each tool based on whether it substantially advances your core professional and personal goals, rather than adopting any tool that offers any possible benefit. This framework is the conceptual weapon against social media's default adoption.