After detailing which land-animals, fish, and fowl are permitted for Jewish consumption, G‑d instructed Moses to teach the Jewish people the laws of ritual defilement. The purpose of these laws is to emphasize that, as Jews, we must value and emphasize life in this world, distancing ourselves from contact with the negativity and depression associated with death. Ritual defilement is contracted either through contact with a dead animal or person, or through some bodily condition that takes the individual close to the boundary between life and death. Contracting ritual defilement prevents an individual from entering the Tabernacle and/or consuming sacrifices and other types of ritually sacred food.
Avoiding Being Duped
לְהַבְדִּיל בֵּין הַטָּמֵא וּבֵין הַטָּהֹר וגו': (ויקרא יא:מז)
[G‑d instructed Moses to teach the Jewish people how] to distinguish between the defiled and the undefiled. Leviticus 11:47

Spiritually, this decree refers to making the moral distinction between what is acceptable, healthy behavior and what is not. This distinction is easy enough when matters are clear and obvious. But all too often, the distinction is blurred, and what is in fact defiled can easily be taken as being undefiled.

By studying the Torah, we remain connected to G‑d, who is not subject to the limited reach of human intellect. Thus attuned to Divine consciousness, we instinctively know what is spiritually healthy and what is not.1