As I mentioned in a previous review, using the "theological giants" as a source of authority can be problematic.  

Martin Luther, for example, is often quoted as saying fewer than "one in a thousand" men are truly suited for celibacy. 

But I ran across a humorous quote from the same work,  The Estate of Marriage:

To sum the matter up: whoever finds himself unsuited to the celibate life should see to it right away that he has something to do and to work at; then let him strike out in God's name and get married. A young man should marry at the age of twenty at the latest, a young woman at fifteen to eighteen; that's when they are still in good health and best suited for marriage. Let God worry about how they and their children are to be fed. God makes children; he will surely also feed them. Should he fail to exalt you and them here on earth, then take satisfaction in the fact that he has granted you a Christian marriage, and know that he will exalt you there; and be thankful to him for his gifts and favours.

Would anyone consider this sound advice on marriage in our current context--telling young women to marry at 15?  I sincerely doubt it.

In fairness to Luther, it was a different time--men were finished with their education (if any) much earlier.  But that's my point--we must be careful in interpreting and applying his thoughts. 

Don't get me wrong--I think we can still learn much from those who have gone before us and wrestled with theological issues.  But let's not forget something: even "theological giants" were only men.