Introduction: Trust is of all times. It is pervasive and indispensable. It is also open to treachery, and blind, unconditional trust is unwise. Trust is a complex and slippery notion. Many of its intricacies have been recognized throughout history. Behavioural science, however, has had problems in tackling the concept. Social science neglected it until some thirty years ago. Economics has begun to recognize the importance of trust but tends to underestimate its complexity and to misconstrue it. A proper understanding of trust requires that we cross the boundaries of economics and include sociological and social-psychological insights. Trust is inherently social, in that it has interaction between people as both its object and its source. Trust should be seen as a process, where it is both the outcome of interaction and the basis for it.

In the last thirty years the sociological and management literatures have produced a kaleidoscope of insights, which now require some ordering for the sake of clarity and analytical grip. This chapter contains elements from a recent book (Nooteboom 2002) in which I aimed to contribute to more conceptual coherence, without surrendering useful subtleties. There are different definitions of trust in the literature. Trust entails a variety of objects, or things one can have trust in. One important question concerns the relation between personal and organizational trust. One can have trust in different aspects of behaviour, and trust may vary with the conditions of behaviour. In sum, trust is a four-place predicate: the trustor (1) trusts the trustee (2) in some aspect of behaviour (3), under some conditions (4). Trust also has a variety of foundations or sources. Trust may be based on a rational inference of trustworthiness, which provide the reasons for trust. It also has psychological causes of trust. This chapter proceeds as follows. The second paragraph attempts to clarify some basic features of trust: the value, definition, objects, and aspects of trust. The third paragraph turns to the sources of trust: the foundations and inference of trustworthiness, and the limits of trust. The fourth paragraph gives a further analysis of the process of trust development. The fifth paragraph gives conclusions.