有關「は」與「が」差異處之既往研究,有下列五種:已知與未知的理論、現象句與判斷句的理論、句與子句的理論、對比與排他的理論、假定與指定的理論。確實,此五種理論,都能夠做為獨立的理論。而這五種理論中是否有共通處?從「は」與「が」表現主語的句子來探討,「は」與「が」都能視其為主語。但精確來說,「は」為主題,「が」是主語。「は」接在整體(大物件)之後;「が」接在整體中的一部分(小物件)之後。此五種理論的共通點為「『は』具有強大的強韌性,而『が』弱而小」。也就是說, 此五種理論共通的要素為「『は』的影響範圍很廣,『が』的影響範圍很小」。以一句話來說,「『は』是大的,『が』是小的」。筆者將此稱為「は」與「が」的大小理論。此「は」與「が」的大小理論為筆者獨創的理論。
There are five theories in regards to the differences between "は" and "が" in previous studies: the theory of known and unknown, the theory of phenomenon and statement sentences, the theory of sentences and clauses, the theory of contrast and exclusivity, and the theory of presumption and designation. Indeed, each of the five theories stands for an independent theory. However, is there any common point? Discussing a sentences with "は" and "が" as subjects, both can be regarded as subjects; but precisely speaking, "は" is the topic and "が" the subject. "は" is attached to the entire body (large object) while "が" is attached to a part of the entire body (small object). The common point in these five theories is that " 'は' has powerful strength and toughness and 'が' is comparatively weak and small". It also means, the common element of these five theories is that " 'は' makes intense influences while 'が' makes little impacts". In a word, " 'は' is large and 'が' is small". This is the innovative large-small theory regarding "は" and "が" developed by the author.