At one time, when very few were literate, the use of symbolism was widespread. It was a form of 'visual shorthand' which suggested abstract concepts as well particular stories. Symbols were easily recognised, and understood, but literacy increased the need for symbolism declined. In centuries past, symbols, especially religious symbols, were common throughout Christendom. It did not matter where one lived, one would recognise most, if not all, of the symbols although there were, of course, local variations. When a series of symbols were associated a whole string of ideas could be conveyed. At the simplest level symbols could be used to relate a story, a parable, an event by grouping, in sequence, a number of symbols. At the most complex level a Cathedral (itself a Christian symbol) contains thousands of individual symbols which, in combination, present a vast range of parables, theological concepts and even debates. In this more secular world the use of, and the understanding of, symbolism has been and continues to be reduced.
 
This has had the effect of allowing every individual to place their own particular interpretation and meaning on symbols which at one time had only one or two accepted interpretations. This is a particular problem with places such as Rosslyn Chapel where everyone, and his or her dog, can suggest the meaning, purpose and importance of its symbolism whereas at one time such a huge diversity of interpretations would simply not have applied.

For More: http://www.rosslyntemplars.org.uk/symbolism.htm