The "four principles approach" has been popularly accepted as a set of universal guidelines for biomedical ethics. Based on four allegedly trans-cultural principles (respect for autonomy, nonmaleficence, beneficence and justice), it is supposed to fulfil the need of a 'culturally neutral approach to thinking about ethical issues in health care'. On the basis of a case-history, this paper challenges the appropriateness of communicating in terms of these four principles with patients with a different background. The case describes the situation in which Muslim parents bring forward that their religion keeps them from consenting to end-of-life decisions by non-religious paediatricians. In a literature analysis, the different meanings and roles of the relevant principles in non-religious and Islamic ethics are compared. In non-religious ethics, the principle of nonmaleficence may be used to justify withholding or withdrawing futile or damaging treatments, whereas Islamic ethics applies this principle to forbid all actions that may harm life. And while the non-religious version of the principle of respect for autonomy emphasises the need for informed consent, the Islamic version focuses on "respect for the patient". We conclude that the parties involved in the described disagreement may feel committed to seemingly similar, but actually quite different principles. In such cases, communication in terms of these principles may create a conflict within an apparently common conceptual framework. The four principles approach may be very helpful in analysing ethical dilemmas, but when communicating with patients with different backgrounds, an alternative approach is needed that pays genuine attention to the different backgrounds.