The abundant availability of raw materials in nature is the gift of God to humanity. The invention of technologies to convert raw materials into useful products is the contribution of science to modern civilization. Scientific principles and laws of nature broadly dictate the conversion of materials into components and, thus, the performance of the components in an engineered product. Disregard for these laws and principles leads to deficiencies in design, manufacture and maintenance. The deficiencies may be flaws or defects; these two faults are often incorrectly considered to be synonymous. While a flaw is a deviation from the perfect, a defect is a deviation from the acceptable. All the defective parts are flawed, but very few flawed parts are defective. Similarly, all defects need not result in failure, but all failures originate at defects. It is, therefore, necessary to identify the nature and source of the defects, which ultimately cause failures in service.