A "no ethics" principle has long been prevalent in science and has demotivated deliberation on scientific ethics. This paper argues the following: (1) An understanding of a scientific "ethos" based on actual "value preferences" and "value repugnances" prevalent in the scientific community permits and demands critical accounts of the "no ethics" principle in science. (2) The roots of this principle may be traced to a repugnance of human dignity, which was instilled at a historical breaking point in the interrelation between science and ethics. This breaking point involved granting science the exclusive mandate to pass judgment on the life worth living. (3) By contrast, respect for human dignity, in its Kantian definition as "the absolute inner worth of being human," should be adopted as the basis to ground science ethics. (4) The pathway from this foundation to the articulation of an ethical duty specific to scientific practice, i.e., respect for objective truth, is charted by Karl Popper's discussion of the ethical principles that form the basis of science. This also permits an integrated account of the "external" and "internal" ethical problems in science. (5) Principles of the respect for human dignity and the respect for objective truth are also safeguards of epistemic integrity. Plain defiance of human dignity by genetic determinism has compromised integrity of claims to knowledge in behavioral genetics and other behavioral sciences. Disregard of the ethical principles that form the basis of science threatens epistemic integrity.