We continue our exploration of constructor theory, our deepest theory in physics. We learn about the conceptual tools used in the theory, such as constructors, tasks, and substrates. We explain how constructor theory solves a few philosophical problems, such as whether or not causation is real, and what knowledge is in physical terms. We explain why constructor theory expresses knowledge as a fundamental quantity in Reality. Finally, we define a universal constructor and suggest that future research may prove the possibility of its creation.
