14 minutes ago, drpaladin said:

Doubt can be healthy

.

Brings to mind, curiosity killed the cat...........

Just the facts:

DOUBT Definition & Meaning - Merriam-Webster

DOUBT Synonyms: 47 Similar and Opposite Words | Merriam-Webster Thesaurus

DOUBTFUL Definition & Meaning - Merriam-Webster

The Doubt | Definition & Meaning - Merriam-Webster

A Doubt | Definition & Meaning - Merriam-Webster

DOUBTLESS Definition & Meaning - Merriam-Webster

and just in case you have ever wondered?

DOUBTING THOMAS Definition & Meaning - Merriam-Webster

"Doubt" comes from the Latin dubitare (meaning to hesitate or be uncertain), which is tied to duo ("two").  It means "to be of two minds" or to be undecided between two choices.  It got to English through the Old French douter or doter (meaning to fear or doubt).  In Middle English it was douten.  The silent "b" in "doubt" was artificially inserted into the English spelling during the 16th century. Early modern English scholars and spelling reformers added it to make the English word visibly reflect its original Latin root (dubitare), even though the "b" was never actually pronounced. 

According to the Oxford English Dictionary (OED), the word "doubt" was first used in English during the Middle English period (1150-1500).  The earliest recorded use of the noun form is before 1225 in the Legend of St. Katherine.  The earliest recorded use of the verb form is around 1225 in the Ancrene Riwle, a guide for monastic women.  In early English, the word was often used to mean "fear" or "dread", in addition to uncertainty.   The OED’s earliest documented evidence for the word doubtful dates to around 1397–1398 in Gregory's Chronicle.  The OED finds its first recorded appearance of doubtless was in the writings of Geoffrey Chaucer, widely known for The Canterbury Tales.  According to the OED, the adjective "doubting" was first recorded in writing around 1425 appearing in the works of the Scottish historian and prior Andrew of Wyntoun.