The question explored in this book is how contracts can manage uncertainties.Commercial parties face uncertainties on a regular basis.Market fluctuations, new laws and regulations, pandemics, rapid technology advancements, and geopolitical tensions are all examples of events whose nature cannot be easily foreseen or captured by the contractual parties’ expectations.One possible way of addressing the uncertainty generated by such risks and events is through reliance on established contractual doctrines, such as variation or frustration.Under English law, these doctrines are traditionally limited.Another, and typically preferable, method is for contract drafters to include clauses that modify, suspend, or terminate the obligations or liabilities of one (or both) of the parties, or clauses that at least open up the options for renegotiation.Examples include material adverse change (or effect) clauses, hardship clauses, performance clauses, termination or suspension clauses, remedies clauses, and variation clauses. Such clauses raise a range of issues concerning their interpretation, effect and enforceability; the consequences that follow when the clauses do not work as planned; the consequences of allocating contractual discretion to a party to determine the existence of the relevant risk or event; and the extent to which the existence of specific clauses changes the options available to the parties beyond what general contract law principles offer. The book advances the understanding of how the law deals with the unexpected and is an essential read for academics, students, and practitioners, including contract drafters, legal advisors, and litigation lawyers.