Warren and Brandeis write that privacy rights should protect both businesses and private individuals. They describe rights in trade secrets and unpublished literary materials, regardless whether those rights are invaded intentionally or unintentionally, and without regard to any value they may have. For private individuals, they try to define how to protect "thoughts, sentiments, and emotions, expressed through the medium of writing or of the arts". They describe such things as personal diaries and letters needing protection, and how that should be done: "Thus, the courts, in searching for some principle upon which the publication of private letters could be enjoined, naturally came upon the ideas of a breach of confidence, and of an implied contract". They also define this as a breach of trust, where a person has trusted that another will not publish their personal writings, photographs, or artwork, without their permission, including any "facts relating to his private life, which he has seen fit to keep private". And recognizing that technological advances will become more relevant, they write: "Now that modern devices afford abundant opportunities for the perpetration of such wrongs without any participation by the injured party, the protection granted by the law must be placed upon a broader foundation".