As a young boy I would often construct card buildings. I would start with three cards as my base and the wall of a particular room as the forth side of the base. I then would lay two cards on top of the three vertical card pieces. I would try to see how high my card building would go before it crumbled. I sometimes could get three to four floors before the structure became too week to stand. Each floor was more precarious because the new foundations became increasingly weak as the cards went up. Without the initial foundation of carpet to solidify the base cards, it would have been impossible to even construct the first floor.
The foundation was crucial for my card structure to even be erected. A foundation is necessary for any structure to go up. Similar to structure in architecture is the necessity for foundationalism in truth. Foundationalism is, "The theory of knowledge that affirms the need for certain foundational principles as the basis of thought."  Simply put, foundationalism argues that knowledge of truth is not possible without these principles (called first principles, such as the law of non-contradiction). Foundationalism ties directly into truth, for without a foundation, truth has nothing to stand on.
Christian apologist, Ravi Zacharias was once taken to what was referred to as the first post-modern building. This building was held in high esteem because of its randomness in design according to the architect. One of the main tenants of post-modernism is that truth is relative or truth has no foundation to stand on. If truth is relative, then truth cannot be known, but when one says truth is relative she is using foundational talk. In essence, relative truth turns out to be contradictory, because the statement that truth is relative is based on a foundational principle while at the same time being denied by the statement. Without a foundation it is impossible to know truth. Ravi Zacharias rightly inquired about the foundation, because without the foundation, you have no building. To make matters worse the architect further contradicts himself by saying he had "no design in mind." 
Truth must rest upon a foundation or there is no way to know the truth. Truth by its very nature is exclusive and must correspond with reality. When building my card structures of the past, it would have been impossible to construct a single wall without a foundation. Similarly, relative truth is a like a foundational - less structure. A truth without a foundation doesn't just cause your house of cards to fall, but it becomes impossible to build in the first place.
 Geisler, Norm, Encyclopedia of Christian Apologetics, p. 259
 Postmodern Architecture