The classical electromagnetic field exhibits macroscopic quantum coherence. Quantum decoherence is the loss of quantum coherence. We consider four examples of temporal coherence. Common sense assesses narrative coherence and fidelity. One of the first methods used to measure the coherence of a laser was interferometry. The principle of OCT is white light, or low coherence, interferometry. Some argue this shift was essential to bringing theoretical coherence to Jung's earlier work. They satisfy Glauber's quantum description of coherence. Ignosticism concerns belief about God's conceptual coherence. Holography requires light with a long coherence time. The above conditions satisfy the Write Propagation criteria required for cache coherence. Cloud computing relies on sharing of resources to achieve coherence and economies of scale. This article focuses on the coherence of classical electromagnetic fields. A precise definition is given at degree of coherence. It is related to the broader concept of coherence.