In the course of psychotherapy, psychologists need to make important clinical decisions regarding treatment goal selection, measurement procedures, and treatment methods. These decisions can be made without regard to the epistemic and ethical responsibilities that accompany professional status. Epistemic duties are obligations to obtain and have knowledge, while ethical duties are obligations to apply this knowledge accurately. We argue that these epistemic and ethical responsibilities are invoked and can be adequately addressed in the informed consent process. When the informed consent process is violated or done poorly, our epistemic and ethical responsibilities are not met and the client may be harmed. We argue that what the public assumes it is buying from us (and what we purport to sell) are specialised knowledge and skills; when psychologists are not meeting their epistemic duties, what our clients are receiving instead is intuition and performance art. We discuss errors that occur in the course of psychotherapy, as well as how we as professionals must seek to reduce or eliminate them.