There's one uneasy borderline between what is external and what is internal, and this borderline is defined exactly by the sense organs and the skin and the introduction of external things within my own body. Consciousness is altered by physical events and physical objects, which impinge upon my sense organs, or which I introduce into my body.
Now the name traditionally given to external objects or processes which change you internally is sacrament. Sacraments are the visible and tangible techniques for bringing you close to your own divinity.