These three interdependent factors combined add up to Understanding and are expressed as a triangle. ARC is a fundamental principle of the Scientology religion. The first corner of the triangle is affinity, which is the degree of liking or affection for someone or something.
Reality is the second corner and is, fundamentally, agreement.
The third corner is communication, defined as the interchange of ideas between two people. All three of these elements are interrelated. Without a degree of liking and some basis of agreement there is no communication. Without communication and some basis of affinity, or emotional response, there can be no reality. Without some basis for agreement and communication, there can be no affinity.