Final answer:
The only known portrait of Shakespeare during his lifetime is the engraving by Martin Droeshout in the 1623 First Folio of Shakespeare's plays, which is considered authentic as it was approved by those who knew him.
Step-by-step explanation:
The only known portrait of Shakespeare painted during his lifetime is believed to be the engraving done by Martin Droeshout, which appeared in the First Folio of Shakespeare's plays published in 1623. This engraving is particularly significant because it was created posthumously but endorsed by people who actually knew Shakespeare, suggesting its authenticity. It's interesting to note the rarity of portraits during this period; they were significant indicators of status, and not everyone could afford the luxury of having their likeness captured. Art, during the Renaissance and beyond, was a matter of significant prestige and expense. As for identifying painters from history, art historians have attempted to attribute various works to specific artists. The process can be intricate and uncertain, as styles can be imitated and origins disputed.