bedrock

bedrock
bed‧rock /ˈbedrɒk $ -rɑːk/ noun
1. [singular] the basic ideas, features, or facts on which something is based:
    Marriage and children are the bedrock of family life.
2. [uncountable] solid rock in the ground below soil or sand
     

THESAURUS

   ▪ basis the facts, ideas, things etc from which something can be developed: His work will be used as a basis for future research.
   ▪ foundation the thing on which something is based, especially something important that continues for a long time: Their ideas were the foundation for the political system that exists in the UK today. | How can we provide a solid foundation for world peace?
   ▪ bedrock the most important thing that something depends on in order to be successful: Honesty is the bedrock of any healthy relationship. | Labour’s traditional bedrock of support is among the working classes.
   ▪ cornerstone the most important thing that something depends on in order to be successful, especially in business and politics: Confidence is the cornerstone of our business. | NATO remains a cornerstone of defence policy for Europe.