Ayn Rand argued that there is a positive harmony of interests among free, rational humans, such that no moral agent can rationally coerce another person consistently with his own long-term self-interest. Rand argued that other people are an enormous value to an individual's well-being (through education, trade and affection), but also that this value could be fully realized only under conditions of political and economic freedom. According to Rand, voluntary trade alone can assure that human interaction is "mutually" beneficial. Rand's student, Leonard Peikoff has argued that the identification of one's interests itself is impossible absent the use of principles, and that self-interest cannot be consistently pursued absent a consistent adherence to certain ethical principles. Recently, Rand's position has also been defended by such writers as Tara Smith, Tibor Machan, Allan Gotthelf, David Kelley, Douglas Rasmussen, Nathaniel Branden, Harry Binswanger, Andrew Bernstein, and Craig Biddle.