Here are some key ideas from Agrippa's "Three Books of Occult Philosophy":
The universe is made up of four elements: earth, air, fire, and water.
There is a correspondence between the macrocosm (the universe) and the microcosm (the individual), and knowledge of this correspondence can be used to affect change in the world.
The practice of magic involves the use of symbols, rituals, and invocations to manipulate natural forces and bring about desired outcomes.
Astrology is a tool for understanding the movements of the planets and stars and their influence on human affairs.
Theurgy is a form of magic that involves invoking divine or angelic beings to achieve spiritual goals.
Knowledge of the divine names and the use of numerology are important components of magic and can be used to unlock hidden knowledge and power.
The soul is immortal and can be liberated from the physical body through spiritual practice.