Sharp invented this rule after he noticed this particular construction (sometimes called a "Sharp's construction") was used with "God" and "Christ" in 5 places in the NT. If he could convince others that his "rule" was true, then they would think there was finally (after 1400 years of a "trinity" tradition) absolute grammatical Bible proof that God and Jesus are the same "person"!
One of the 5 "proofs" of Jesus' Godhood according to Sharp is found at Eph. 5:5.
... en th basileia tou cristou kai qeou [symbol font]
"...in the kingdom of the Christ and God"
Since the first noun ("Christ" here) has the article ("the") with it and the following noun ("God" in this scripture) does not have the article ("the"), then (according to Sharp) God and Christ are the same person!
There are a number of reasons why Sharp's Rule, as applied to these 5 "proofs," is invalid. One important strike against it is the fact that even many respected trinitarian NT grammar experts and translators have rejected it as a valid rule - e.g., see G. B. Winer; J. H. Moulton; C. F. D. Moule; Dr. James Moffatt (see Titus 2:13; and 1 Tim. 5:21); Dr. William Barclay (2 Thess. 1:12); and Roman Catholic scholar Karl Rahner (2 Peter 1:1).
For example, examine the following trinitarian Bible's renderings of these "Sharp's Constructions":
Eph. 5:5 - KJV; KJIIV; RSV; NRSV; LB; MLB; NIV; NEB; REB; GNB; TEV; NAB (`70,'91).
2 Tim. 4:1 - most trinitarian Bibles.
1 Tim. 6:13 - all trinitarian Bibles.
These many respected Bibles, translated by expert trinitarian New Testament scholars, clearly disregard Sharp's "Rule" at these (and other) places and show two persons being spoken of!
Notice Eph. 5:5, for example. Most trinitarian Bibles translate this example of Sharp's Construction: "in the kingdom of Christ and of God" - KJV; NRSV; RSV; NIV; NEB; REB; NAB; Douay; MLB; LB; GNB; TEV; The Amplified Bible; Third Millenium Bible; New Living Translation; New Century Version; God's Word; Holman Christian Standard Bible; Wesley's New Testament; Phillips; and the Webster Bible. This is not the way it would be translated if the two descriptions were of the same person! (At the very least it would be rendered more literally as "the kingdom of the Christ and God.") Instead it clearly shows two persons!
So, although we can find such constructions as "the king and master of the slave" where the first noun (with the definite article, `the') is the same person as the second noun (without the definite article), there is no grammatical reason that this must always be so. Such constructions as "the boy and girl" and "the President and Vice President" (found in Amendment XX [as ratified in 1933] of the Constitution of the United States of America), which refer to more than one individual, are just as grammatically correct in both English and NT Greek.
For much more concerning Sharp's Rule, see: