The biennial Mallet-Milne Lecture was inaugurated by the Society for Earthquake and Civil Engineering Dynamics (SECED) in 1987 to commemorate the lives of two British pioneers in the fields of earthquake engineering and seismology: Robert Mallet (1810-1881) and John Milne (1850-1913). In the sixth lecture, at the Institution of Civil Engineers in London in May 1997, Professor Roy Severn took forward the debate on the effective reconsiliation of theoretical (analytical) and experimental (field and laboratory) models. His experience gained over a lifetime in structural idealisation and modelling, has followed the design and assessment process of loading characterisation, dynamic material property selection, structural response prediction and comparison to code and other acceptance criteria. This book provides a concise summary of the key issues in reconsiliation.