This article shows how new theoretical work on assessing sustainability of farms, carried out as part of a multidisciplinary approach, allowed a new theoretical framework to be develop, along with version 4 of the IDEA Method (Indicateurs de Durabilité d'une Exploitation Agricole). The first section divides existing studies taken from the literature into two types of indicator-based conceptual frameworks: those based on sustainable agriculture objectives, and those based on a systemic approach focusing on the properties of sustainability as applied to agriculture. The second part of this article explains the overall process of assessing farm sustainability based on the conceptual framework developed for IDEA v.4. The theoretical framework relates to strong sustainability, and agricultural multifunctionality (with 12 associated objectives). The method includes a systemic analysis of sustainability based on five properties observed within a sustainable farm: The ability to produce and reproduce goods and services; Autonomy; Robustness, Territorial embeddedness and Overall responsibility. These properties are then evaluated from 54 different indicators of agricultural sustainability. The method combines two mutually complementary approaches to assessing sustainability. The first of these examines the extent to which sustainability has been achieved (in agro-ecological, socio-territorial and economic terms) by aggregating indicators based on 13 components and a scoring system using sustainability " units ". The second approach assesses the level of sustainability based on the five properties mentioned above. Indicators are aggregated hierarchically and organised based on 14 key categories. We show how the concept of properties has real educational value and can help to bring a new perspective to the field of sustainable farming.