Este artículo es un comentario crítico a un artículo de David Widerker previamente aparecido en la misma revista, el Journal of Philosophy. En este artículo, Widerker sostenía, frente a sus posiciones anteriores, que era posible construir contraejemplos efectivos, en la línea iniciada en los años sesenta por Harry Franfurt, al llamado 'Principio de Posibilidades Alternativas'. El núcleo de mi crítica a Widerker consiste en negar que los agentes, en sus pretendidos contraejemplos, sean moralmente responsables de su decisión, debido a que no son capaces de responder apropiadamente a razones morales. This paper is a critical comment on an article of David Widerker which also appeared in the Journal of Philosophy. In this article, Wideker held, against positions previously defended by him, that in was possible to design effective counterexamples, in the line initiated by Harry Frankfurt in 1969, to the so-called 'Principle of Alternative Possibilities'. The core of my criticism of Widerker is to deny that agents, in his putative counterexamples, are morally responsible for their decisions, owing to the fact they are not able to respond appropriately to moral reasons.