Final answer:
The book 'Dianetics: The Modern Science of Mental Health' was published in 1950 by L. Ron Hubbard and became the basis for the Church of Scientology.
Step-by-step explanation:
The book published in 1950 that became the foundation for L. Ron Hubbard's religion is Dianetics: The Modern Science of Mental Health. This book laid the groundwork for the Church of Scientology, a movement that began as a set of ideas and practices regarding the metaphysical relationship between the mind and body.
Hubbard's work introduced the concept of auditing, a process intended to clear individuals of negative past experiences and traumas, leading to a higher state of spiritual awareness known as Clear.