Most of the reports on synthetic biology include not only familiar topics like biosafety and biosecurity but also a chapter on 'ethical concerns'; a variety of diffuse topics that are interrelated in some way or another. This article deals with these 'ethical concerns'. In particular it addresses issues such as the intrinsic value of life and how to deal with 'artificial life', and the fear that synthetic biologists are tampering with nature or playing God. Its aim is to analyse what exactly is the nature of the concerns and what rationale may lie behind them. The analysis concludes that the above-mentioned worries do not give genuine cause for serious concern. In the best possible way they are interpreted as slippery slope arguments, yet arguments of this type need to be handled with care. It is argued that although we are urged to be especially vigilant we do not have sufficiently cogent reasons to assume that synthetic biology will cause such fundamental hazards as to warrant restricting or refraining from research in this field.