法學的實證研究雖於近年受到國內法學界的重視，然而一方面，受限於國內法學界對規範論證的想像，多半仍深受概念法學與評價法學的影響，而堅守「法∕事實」、「應然∕實然」的二分，並認為（誤解）在法與應然場域中的規範論證無法從對「實然」的考察中獲得解答，而僅能從語意學上的邏輯演繹，或者從司法者對「應然」的價值理解裏探詢；另一方面，也由於法學這種研究「規範」的學科，與研究「經驗現象」的實證科學間，存在著某種因研究對象不同而產生的緊張關係，使得在規範論證中所由依據的經驗性事實基礎為何的課題，往往未受重視，而援引實證研究進行規範論證，也未受到法學界的誠心接納。連帶影響使得國內的法學實證研究主題，多半與法學本身的規範論證保持相當的距離感。在此一認識脈絡下，本文將嘗試指出，國內學者將最有可能連結法學規範論證與實證科學研究的「立法事實」(legislative facts)概念，單純理解為國會立法者（或制訂法規命令的行政機關）制訂法律（或法規命令）所由依據的社會生活事實，並進而暗示司法者對「立法事實」的調查、認定與審查，僅止於以諸如比例原則等審查基準對此等法令進行法規違憲審查時始發生。對「立法事實」的此一狹隘理解，掩蓋了法規違憲審查以外一般的規範論證，無論在其內部證立或外部證立的過程，都可能須要建立在某些經驗性事實基礎之上。同時，此種將「立法事實」單純視為法規違憲「審查標的」之一部分的理解，也因為將焦點置於處理不同違憲審查審查標準∕密度下事實證明度(standard of proof)的問題，而忽略了論證上一些更根本的前提問題。一旦「立法事實」之概念可以還原為「規範論證中所由依據的經驗性事實基礎」，並使之從違憲審查標準∕密度的操作課題中解放出來，在規範論證中透過實證科學提出並檢證「經驗性事實基礎」的模式，才得以更常態地在法學論證中被實踐。當然，針對實證研究背後所隱含之價值預設進行檢驗的必要性，以及對自然主義之謬誤的警覺，仍不應因此種常態化而有所改變。反之，「援引實證科學進行規範論證」的常態化，將促使吾人得以對事實隱含價值與價值依賴事實的辯證關係，進行更深刻的反省。

While great attention has been in recent years paid to empirical studies in Taiwan's legal academy, the use of scientific evidence in the studies of law from what Ronald Dworkin called the ”internal point of view” is still scant. The forefront of the new fashion is rather limited to the studies about law from the ”external point of view.” The reason behind this unfounded disparity is due largely to, this article argues, an untenable brand of the distinction between ”fact” and ”law” and a misunderstanding about the is-ought problem. The misconception that questions of law cannot be answered (externally justified) by ”fact” but ”law” itself has infected the reception of the concept of ”legislative fact” in Taiwan. The ”legislative fact” is in Taiwan understood and treated merely as the ”object” of the constitutional review just like a legislation that is under review. The focus of legal scholars in discussing the concept of ”legislative fact” is therefore limited to the problem of whether and to what extent it is justifiable to substitute judicial judgment of facts for that of the legislature. The function of ”legislative fact” to externally justify a legal norm is, however, entirely ignored. This article uses the J.Y. Interpretation No. 584 as an example to illustrate that the current problem of making use of empirical evidence in legal reasoning is not that those who do so commit naturalist fallacy, but that they very often fail to follow some basic logic rules. More importantly, they fail to recognize the function of empirical studies to externally justify a legal norm, for example, a new conception of equal protection, which this article argues is the real answer to what has bewildered the Justices in the case of J.Y. Interpretation No. 584.