"A priori" example
Jennifer hates eating vegetables. Although she really likes the smell of tomatoes, she has always believed, a priori, that tomatoes are vegetables and thus has never tried them. If Jennifer ever discovers that scientists classify tomatoes as fruit, she might very well change her mind and eat a tomato.
During the course of a trial, Lawyer Ricky has repeatedly angered the judge by arriving late and offering silly excuses for his tardiness. Today, Lawyer Ricky has a good excuse: he was the victim of a mugging on his way to work and is recovering in the hospital. However, since nobody notified the court, the judge has concluded, a priori, that Lawyer Ricky has once again neglected his responsibility to show up on time and will offer up a laughable excuse as soon as he comes in.