Academic freedom is designed to serve society by making possible the free exchange of ideas and information and subjecting them to such criticism. Only in this way can knowledge be advanced. For that to take place, teachers and scholars must be able to pursue the truth without fear of reprisal. Tenure is a means to that end. It is not automatic.
Tenure is extremely hard to earn.
It follows an extended period, usually up to seven years, in which the faculty member's performance in teaching, scholarship, and service to the institution is assessed. At the U of I, fewer than half the junior faculty hired get tenure. The probationary period is well in excess of what is required by most labor union contracts outside higher education and most civil service systems. Just as faculty members must observe these standards individually, so must the tenured faculty uphold and enforce them corporately. Tenure is more than simple job security.