張東蓀可能是最有資格在「科學論戰」中公開支持張君勱的哲學家，但他卻在「科玄論戰」爆發前後不久，與張君勱進行了一場針鋒相對，哲學意味極濃，且幾乎只限於人生與知識問題的內部論戰。這是「科玄論戰」討論中一向被忽視的重要層面之一。從微觀且概而言之，本文所談的二張間辯論的重大歧異是，張東蓀的看法是主智主義，而張君勱的則是非主智主義，甚至是反智主義。二張根本的差異，至少在我討論的範圍內，甚至可以歸到二人對科學和理性的態度。 對此時的張東蓀而言，知識即生活，而此時的張君勱則認為知識至多或只能是生活的一部分。張君勱是從本體論或形而上學的觀點著眼，而張東蓀則是從認識論觀點著眼。後者是比較謹慎的態度，但卻得出一樣深遠的結果。若張東蓀只是從不同出發點得出不同的結論，則殊不足為怪。事實卻是，張東蓀不但從認識論推翻張君勱的看法，而且更有意義的是，張東蓀也從生活派哲學的矛盾來指出生活派本身的問題。這是以子之矛攻子之盾的做法。 張東蓀堅稱，「知識無外，與思想即生命」，並告訴我們這種立論並非他自我作古。他並引漢爾唐的《相對律之王國》(J.B.S. Haldane, The Reign of Relativity, pp.146-147)來說明：「知識毋寧是傳具的性質，所有的任何形式的存在皆得與指涉它。尤其不清楚的是，真際可以和意義相分離。知識看起來並不是呆定的東西，但它的實在只在於做為動的歷程，並在性質上與任何外在的事物之間的歷程是完全不同的。因為知識在它本身之創造區分，並且除了通過知識以及知識的條件為條件外，對認知主體的我和我所關涉的事物而言，並沒有可理解的意義可被發現。所以知識變成了先於真際之事體，而像柏格森的「生力」或叔本華之「意志」，本身是最終的真際，不能以它本身以外的條件來表示，就好像創造在它的範圍外是無意義的一樣。」張東蓀的「我們茍掃除一切關於生活的謬見必見思想（知識）的發展就是代表生命，而生命的特徵亦就是知識（思想），除此以外別無生活。」即是本文長篇敘述的重點，也是張東蓀與張君勱兩人在「科玄論戰」爆發前後私底下爭鋒相對內部爭論的核心。其實，關於知識（尤其是科學知識）與生活（尤其是人生）的關係問題也是「科玄論戰」的焦點。

Immediately before and after the explosion of the “Controversy over Science and Metaphysics” in March 1923, Chang Chun-mai (Zhang Junmai) and Chang Tung-sun (Zhang Dongsun) were also engaged in a philosophical debate on the relationship between knowing and living. As probably the best qualified person philosophically to support Chang Chun-mai in the ensuing controversy, Chang Tung-sun might not be expected to have carried out this parallel debate with Chang Chun-mai. In fact, the debate has been largely ignored in studies of the controversy, as it is generally taken for granted that the two Changs shared similar ideas. But a closer study will reveal that the personal debate between the two Changs accounts for much of the reasons why Chang Tung-sun could not unconditionally support Chang Chun-mai in the controversy as Chang Tung-sun advocated an intellectualistic epistemology while Chang Chun-mai adhered to an anti-intellectualistic epistemology. In terms of both general orientation and details, the two Changs’ epistemologies have not much in common, which might be attributed to their respective attitudes towards science and reason. For Chang, “knowing is living” while for Chang Chun-mai knowing could at most only form part of living. Chang Chun-mai’s perspective was ontological or metaphysical while that of Chang Tung-sun epistemological. The latter is a more cautious approach though with equally profound results. It should come as no surprise if Chang Tung-sun came to a different conclusion from the divergent perspective; but what is most significant was that he also pointed out the inconsistencies in Chang Chun-mai’s philosophy of living itself. He used a reductio ad absurdum form of logic. Chang Tung-sun said that his insistence on the argument that “there is nothing conceivable outside knowing, and thinking is living” did not begin with him, for he quoted J.B.S. Haldane’s The Reign of Relativity, pp. 146-7, which put forward exactly the same view, namely “[It] (knowledge) is rather in the nature of a medium to which form of existence must be referred. In particular it does not seem clear that reality can be divorced from meaning. Knowledge appears as if it were no static thing, but actual only as a dynamic process, differing altogether in character from any between outside objects. For it creates its own distinctions within itself, and excepting through it and in its terms there is no intelligible significance to be found for either the self that knows or for the objects to which it is related. Knowledge must thus turn out to be the prius of reality, and like the ‘elan’ of Bergson or the ‘will’ of Schopenhauer, itself the ultimate reality, capable of expression in no terms beyond its own, in as much as creation is meaningless outside its scope.” This is the view to which Chang Chun-mai was in violent opposition. The rarely if ever noted starkly divergent views of the two Changs on whether “knowing is living” is the theme of this article, and is also the crux of the debate between the two Changs around the outbreak of the Controversy over Science and Metaphysics, which was in turn to draw many more enthusiastic participants, making it one of the most exciting and profound intellectual controversies in contemporary China.