The validity of science depends on the integrity of the individual scientist. It is often supposed that science is a distinctive process or system externally regulating the individual scientist; an assumption that science is a mechanism into-which data and ideas are fed and from-which valid knowledge emerges. By this view, the individual scientist is not crucial because individual errors, inabilities and (even) dishonesty are all eliminated by various feedback processes. This conceptualisation of science provides individual ‘scientists’ with a free pass to relax the strictness and purity of their personal honesty and motivations. But all and any possible external systems ultimately require the integrity of individuals, and inner integrity cannot be imposed but most come from within. When individuals concerned with science lack personal integrity then other lower, commoner and more powerful motivations will take-over science. The implication is that when a young scientist is learning to be a scientist he cannot simply learn the subject but must also be working on his own personal development: he must develop integrity until it becomes an iron law. In particular he must develop the understanding that: 1. Truth must become an inflexible habit; 2. Science is spiritual; 3. Truth is a transcendent value; 4. Science is not a methodology, but an attitude, a motivation, a way of being; 5. The proper attitude of a scientist to his subject is a kind of love, a devotion to the phenomenon of which understanding is being sought. Therefore, science must be dominated by honest individuals of indestructible integrity. When individual scientists lack or lose self-motivated integrity, then science simply ceases to be.