Tertium quid refers to an unidentified third element that is in combination with two known ones. The phrase is associated with alchemy. It is Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 for "third thing", a translation of the Greek tríton ti (τρίτον τι). The Greek phrase was used by Plato

Plato

Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

 (360 BC), and by Irenæus (c. AD 196). The earliest Latin example is by Tertullian

Tertullian

Quintus Septimius Florens Tertullianus, anglicised as Tertullian , was a prolific early Christian author from Carthage in the Roman province of Africa. He is the first Christian author to produce an extensive corpus of Latin Christian literature. He also was a notable early Christian apologist and...

 (c. 220), who used the phrase to describe a mixed substance with composite properties such as electrum

Electrum

Electrum is a naturally occurring alloy of gold and silver, with trace amounts of copper and other metals. It has also been produced artificially. The ancient Greeks called it 'gold' or 'white gold', as opposed to 'refined gold'. Its color ranges from pale to bright yellow, depending on the...

, a somewhat different sense than the modern meaning.

In Christology

In the Christological debates of the fourth century, it was used to refer to the followers of Apollinaris who spoke of Christ

Christ

Christ is the English term for the Greek meaning "the anointed one". It is a translation of the Hebrew , usually transliterated into English as Messiah or Mashiach...

 as something neither human nor divine

Divinity

Divinity and divine are broadly applied but loosely defined terms, used variously within different faiths and belief systems — and even by different individuals within a given faith — to refer to some transcendent or transcendental power or deity, or its attributes or manifestations in...

, but a mixture of the two, and therefore a "third thing".

In American political history

In American political history, the Tertium Quids

Tertium quids

The tertium quids refers to various factions of the American Democratic-Republican Party during the period 1804–1812. In Latin, tertium quid means "a third something"...

, or Quids, were moderate members of Jefferson's Democratic-Republican Party. The word implies that their political position was apt to embrace true republicanism

Republicanism

Republicanism is the ideology of governing a nation as a republic, where the head of state is appointed by means other than heredity, often elections. The exact meaning of republicanism varies depending on the cultural and historical context...

 and the comparable conservatism

Conservatism

Conservatism is a political and social philosophy that promotes the maintenance of traditional institutions and supports, at the most, minimal and gradual change in society. Some conservatives seek to preserve things as they are, emphasizing stability and continuity, while others oppose modernism...

 of the Federalist Party, particularly on foreign policy. The Quids arose in 1804 during Thomas Jefferson's

Thomas Jefferson

Thomas Jefferson was the principal author of the United States Declaration of Independence and the Statute of Virginia for Religious Freedom , the third President of the United States and founder of the University of Virginia...

 first term in office. They were led by Virginia's John Randolph of Roanoke

John Randolph of Roanoke

John Randolph , known as John Randolph of Roanoke, was a planter and a Congressman from Virginia, serving in the House of Representatives , the Senate , and also as Minister to Russia...

. They stood by the party's original stance for strict construction of the Constitution and opposed Jefferson's pragmatic approach to governing.

In sociology

In sociology, it describes a category of degraded moral consideration.

In Souls of Black Folk, W.E.B. DuBois used the term "tertium quid" to refer to the identity of African Americans in a racist society, where non-white people are viewed as a devalued category between man and animal.

"The second thought streaming from the death (slave)-ship and the curving river is the thought of the older South, the sincere and passionate belief that somewhere between men and cattle, God created a tertium quid, and called it a Negro—a clownish, simple creature, at times even lovable within its limitations, but straitly foreordained to walk within the Veil."

In American law

In American law, it describes a product marketing strategy.

The term is also used in the important Supreme Court

Supreme Court of the United States

The Supreme Court of the United States is the highest court in the United States. It has ultimate appellate jurisdiction over all state and federal courts, and original jurisdiction over a small range of cases...

 case Wal-Mart Stores, Inc. v. Samara Brothers, Inc. 529 U.S. 205 (2000). In this Lanham Act

Lanham Act

The Lanham Act is a piece of legislation that contains the federal statutes of trademark law in the United States. The Act prohibits a number of activities, including trademark infringement, trademark dilution, and false advertising.-History:Named for Representative Fritz G...

 case, the Court, when discussing product packaging vs. product design, referred to the type of trade dress in its earlier Two Pesos decision as "some tertium quid" that may be a mutation of product packaging and product design—a "third thing."

In literature

In literature, it describes an adulterer. Kipling employs the term in "At the Pit’s Mouth," for an adulterer: "Once upon a time there was a Man and his Wife and a Tertium Quid."