以本然界、事实界、可能界、价值界为基本范畴，冯契先生展开了关于本体论问题的思考，这一考察进路体现了本体论、认识论、价值论的统一。然而，在本然界、事实界、可能界、价值界的表述中，事实界和价值界被分别列为不同之"界"，从逻辑上说，"界"表征着本体论上的存在形态或存在境域，与之相应，把事实界、可能界、价值界等存在形态理解为不同的存在之"界"，至少在逻辑上隐含着将其分离的可能。相对于"本然界"、"事实界"、可能界"、"价值界"等"四重"之界的并立，本然世界和现实世界这"两重"世界的互动，体现了另一种形上视域。在"两重"世界中，一方面可以注意到不同存在形态在本体论层面的分别，另一方面也不难看到现实世界的综合性以及不同存在规定的相关性。与"四重"之界说相关的，是对事实本身的理解。历史地看，从罗素、金岳霖到哈贝马斯，对事实的理解，整体上侧重于认识论之域，与之相异，冯契先生同时肯定"事实"包含认识论与本体论二重内涵，这一看法以说明世界和变革世界的关联为其前提。从形上之维看，这种关联同时构成了本然世界向现实世界转化的前提，就此而言，对事实的以上理解在逻辑上也蕴含了承诺"两重"世界的内在趋向，后者对"四重"之界内含的问题，也从一个方面作了某种限定。

FENG Qi's ontology of "four domains", including the domain of things as such, that of facts, that of possibilities and that of values, embodies the unity of ontology, epistemology and axiology. However, when things as such, facts, possibilities and values are put into different ontological "domains", it leads to a logical danger that they would be separated from each other. In contrast, the interaction between the world of things as such and the world of reality in the "two worlds" presents another metaphysical horizon. In these "two worlds", the ontological difference by no means excludes the comprehensiveness of the world of reality and the relevance of different ontological "domains". While philosophers in the history such as Russell, JIN Yue-lin and Habermas mainly understand facts from the perspective of epistemology, FENG Qi emphasizes the ontological dimension as well as the epistemological dimension of "facts". This is based on the correlation between interpreting the world and changing the world. From the perspective of metaphysics, this correlation is the premise of transforming the world of things as such to the world of reality. In this regard, FENG's notion of facts implies the "two worlds", which also overcomes the possible separation in the "four domains" to some extent.