Final answer:
Pepys may have used tobacco during the plague because at the time, substances like tobacco were sometimes considered to have medicinal properties or provide protection against disease. However, there is no explicit evidence detailing Pepys' reasons for tobacco use during the plague. Practices and beliefs about medical treatments were varied during the plague, influencing behaviors like tobacco use.
Step-by-step explanation:
The reason why Pepys may have used tobacco during the time of the plague was not uncommonly perceived during the 17th century when smokable substances were often considered medicinal or as having the ability to ward off disease, although no specific accounts from Pepys precisely confirm this reason. Tobacco, introduced to Europe from the New World, carried a mixed reputation, with some praising its alleged medicinal properties and others condemning it as harmful and intoxicating. Moreover, during epidemics like the plague, tobacco was sometimes thought to offer some protective value against the miasmas or 'bad air' which were believed to carry disease before the discovery of germ theory.
There also existed a heterogenous landscape of medical treatments and beliefs during the time of the plague. Different treatments were attempted to cure or prevent the disease, reflecting the varying medical theories of the time. The usage of tobacco during the plague, whether by Pepys or others, could have been influenced by such medical practices and beliefs prevalent in that era.