Courses in Natural Science are based on these five textbooks:

Universal knowledge
J. Otto Schweizer

The Great Message - is an inspiring introduction to the Great School of the Masters which is that inextinguishable central source of Knowledge of Nature's Moral Laws that has exerted, and continues to exert, a beneficent, constructive, and uplifting influence on the evolution of humanity from spiritual infancy and ignorance to soul maturity and illumination. The Great School of the Masters is that central reservoir from which the world's greatest teachers received their training and commission to bring to humanity the eternal message of life, love, and immortality. Some of the better known representatives are: Jesus, Confucius, Zarathustra, Buddha, Krishna, Pythagoras and Melchizedek. This book explains that the Great School of Natural Science was launched by a representative of the Great School of the Masters to provide the progressive intelligence of this age a current (early 20th century), scientific presentation of the Laws of Nature and impress upon each truth seeker the obligation to take up the task of soul-unfoldment.
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The Great Work - explains how one must live and what one must do to enable oneself to demonstrate the fact of a spiritual life beyond physical death constructively; that any individual who has "the intelligence to know, the courage to dare, and the perseverance to do," may accomplish the Great Work of self-completion, and constructively make a personal demonstration of spiritual life after physical death, while living on the physical plane. It explains how one may "live the life" on this physical plane in such manner as to derive the greatest benefit, and thereby fulfill the purpose of earthly existence.
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The Great Psychological Crime - traces the action of the Destructive Principle of Nature in individual life beginning with the effects of overindulging in what may be termed negative emotions (anger, fear, self-pity, etc.) and a negative lifestyle. It explains the fact that those who seek to prove the fact of a life after physical death through hypnotic and mediumistic (channeling) methods are in fact inviting the Destructive Principle of Nature into their lives. The culminating destructive powers that may be invoked by the individual, consciously or unconsciously, are chillingly described to serve as a strong warning for all who seek truth.
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The Great Known - is of vital interest to all those who are seeking information concerning life on the spiritual planes, and carries a word of comfort and a message of hope to those who have loved ones beyond "The Valley of the Shadow." It describes some of the conditions upon the spiritual planes, and shows that they are as natural- as much a part of Nature - as the physical world in which we now live. It answers many questions about life after death, and fills the reader with a rational hope for her or his own future life.
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Harmonics of Evolution - discusses the Universal Principle of Polarity which operates throughout the four distinct kingdoms of Nature: mineral, vegetable, animal and human. It traces Nature's evolutionary process of individualizing intelligence culminating in the individual man and woman. It declares to the millions of people living today, as well as to those of the generations yet to come, that the relationships between individual men and women are based on the struggle for happiness and that the possibilities for satisfaction and contentment are possible now in this life. It further declares that physical life has immeasurable possibilities which do not exist in the life to come. Thus, in simple and comprehensive language, it explains the purpose of this present life and the advantages of "living the life" while on earth so that one may escape, in the life to come, the consequences of transgressing the Law of Moral Accountability and Personal Responsibility.
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