The world's population is ageing at an unprecedented rate. If an ‘ageing society’ is defined as one where at least 10% of the population is aged 65 years and above, the number of such ageing societies is projected to increase from 59 in 2010 to 138 in 2050 (UN, 2014). By 2050 the world will be home to some 1.5 billion people aged 65 and over, more agedness than the world has ever experienced. Not only are there increasing numbers of ageing societies (Hyde and Higgs, 2016), but some of the already ageing societies are undergoing a process of ‘hyper-ageing’ as their 65 year old and over populations are projected to increase to over 25% of their respective populations, while the proportion of under 65 year olds falls below average replacement rate fertility (Rowland, 2009). These unprecedented demographic changes have fuelled interest in what has been variously called ‘extreme’, ‘deep’ or ‘real’ old age (Leaf, 1982; Degnen, 2007).

As part of this interest in ‘extreme’ ageing, the concept of a ‘fourth age’ has emerged to highlight some of the more unsettling aspects of later life (Higgs and, Gilleard 2015). This concept provides the context for this book, the idea of a feared and impotent old age, and the part that is played by care in realising this imaginary. We begin, in this first chapter, by exploring the various ways that the concept of a fourth age can be understood. Although we focus largely on work carried out since the term was introduced to the literature by Peter Laslett in his seminal work, A fresh map of life (Laslett, 1989, 1996), we also examine some of the earlier research that has served as a precursor to contemporary understandings. We then outline our own conceptualisation of the fourth age, as a social imaginary realised within the collective consciousness of society, and set this in contradistinction to other models that see the fourth age located more firmly within the corporeality and/or chronology of individual persons.