The Fundamental Nature of Resilience of Engineered Systems Dr. Timothy L.J. Ferris Centre for Systems Engineering, Cranfield University, Defence Academy of the United Kingdom Shrivenham, SN6 8LA timothy.ferris@cranfield.ac.uk Eric Specking University of Arkansas Fayetteville, AR 72701 479-575-7780 especki@uark.edu Dr. Scott Jackson Burnham Systems Consulting Los Angeles, CA 92603 949-726-2003 jackson@burnhamsystems.net Dr. Gregory Parnell University of Arkansas Fayetteville, AR 72701 479-575-7423 gparnell@uark.edu Dr. Edward Pohl University of Arkansas Fayetteville, AR 72701 479-575-6029 epohl@uark.edu Copyright © 2018 by Timothy Ferris, Scott Jackson, Eric Specking, Gregory Parnell, and Edward Pohl. Published and used by INCOSE with permission. Abstract. We take the position that an engineered system is a means to enable user capability that provides value to stakeholders and address the question of the fundamental nature of resilience of engineered systems. Therefore, resilience is concerned with the behavior of the system in the face of a disruption, in particular emphasizing the management, through system design of the system behavior and operational capability under disruptive conditions, which include adverse events outside the operational envelope of the system and conditions in which parts of the system have been damaged. We provide a definition of engineered resilience and show an approach to measure engineered resilience. By taking a philosophical approach to the understanding of resilience, we are able to show where resilience fits in the overall task of engineering systems and how this view provides coherence across the various aspects of resilience which is not otherwise provided. Introduction The subject of resilience of engineered systems has become a major research area in recent years. This research has approached all the facets of a subject area that are addressed when a new area of exploration begins. These topics include questions such as, what exactly is engineering resilience, how can a system be made resilient, and how can resilience be measured. These and other topics are important in the process of understanding the nature of resilience and how knowledge of resilience can be used to improve the engineering of systems so that they embody this characteristic, which is commonly believed to be desirable because it leads to increased user capabilities.