Modern philology has shown that "On the World and the Soul" is a pseudepigraphon from somewhere between the early first century BC to the early first century AD, and is based on Plato's "Timaeus", rather than the other way around. The Pseudo-Timaeus employs a simplified mode of reasoning and presentation, presenting conclusions rather than arguments and omitting any dialogue, meaning that it was perhaps intended as a summary of the notoriously difficult original for use in a classroom setting. While it may have originated in part as a set of lecture notes to the Platonic original, it tends to omit difficult sections of the "Timaeus" rather than provide explanations. Some of Pseudo-Timaeus's theses are very hard to understand without knowledge of Plato's work.