Chapter 3 considers the ethical issues raised by research involving vulnerable participants. ‘Vulnerability’ is a concept
that is widely used in research ethics, but it can mean different things. Sometimes vulnerable participants are understood
as those who are unable to give valid consent either due to lack of competence or because of circumstances
which cast doubt upon its voluntariness. The part of the chapter which deals with this extends the previous chapter’s
account of what makes a consent valid and what should be done in cases where valid consent cannot be obtained.
‘Vulnerability’ can also relate to susceptibility to harm or exploitation, and in addressing this Chapter 3 looks ahead
to the discussions of these issues in Chapters 5 and 6.