The following rules are generally given as governing accurate definition. (1) _The definition must be equivalent or commensurate with that which is defined_; it must be applicable to all the individuals included in the concept and to nothing else. Every man, and nothing else, is a rational animal. "Man is mortal" is not a definition, for mortality is predicable of irrational animals. (2) _The definition must state the essential attributes_; a concept cannot be defined by its accidental attributes; those attributes must be given which are essential and primary. (3) _The definition must be per genus et differentiam_ (or _differentias_), as we have already seen. These are the important rules. Three minor rules are: (4) _The definition must not contain the name of the concept to be defined_; if it does, no information is given. Such a proposition as "an archdeacon is one who performs archidiaconal functions" is not a definition. Concepts cannot be defined by their correlatives. Such a definition is known as a _circulus in definiendo_. (5) _Obscure and figurative language must be avoided_, and (6) _Definitions must not be in the negative when they can be in the affirmative_.
[1] "Rational animal" is thus the predicate of the statement constituting the definition. Sometimes the word "definition" is used to signify merely the predicate.
DEFOE, DANIEL (c. 1659-1731), English author, was born in the parish of St Giles, Cripplegate, London, in the latter part of 1659 or early in 1660, of a nonconformist family. His grandfather, Daniel Foe, lived at Etton, Northamptonshire, apparently in comfortable circumstances, for he is said to have kept a pack of hounds. As to the variation of name, Defoe or Foe, its owner signed either indifferently till late in life, and where his initials occur they are sometimes D. F. and sometimes D. D. F. Three autograph letters of his are extant, all addressed in 1705 to the same person, and signed respectively D. Foe, de Foe and Daniel Defoe. His father, James Foe, was a butcher and a citizen of London.
Daniel was well educated at a famous dissenting academy, Mr Charles Morton's of Stoke Newington, where many of the best-known nonconformists of the time were his schoolfellows. With few exceptions all the known events of Defoe's life are connected with authorship. In the older catalogues of his works two pamphlets, _Speculum Crapegownorum_, a satire on the clergy, and _A Treatise against the Turks_, are attributed to him before the accession of James II., but there seems to be no publication of his which is certainly genuine before _The Character of Dr Annesley_ (1697). He had, however, before this, taken up arms in Monmouth's expedition, and is supposed to have owed his lucky escape from the clutches of the king's troops and the law, to his being a Londoner, and therefore a stranger in the west country. On the 26th of January 1688 he was admitted a liveryman of the city of London, having claimed his freedom by birth. Before his western escapade he had taken up the business of hosiery factor. At the entry of William and Mary into London he is said to have served as a volunteer trooper "gallantly mounted and richly accoutred." In these days he lived at Tooting, and was instrumental in forming a dissenting congregation there. His business operations at this period appear to have been extensive and various. He seems to have been a sort of commission merchant, especially in Spanish and Portuguese goods, and at some time to have visited Spain on business. In 1692 he failed for £17,000. His misfortunes made him write both feelingly and forcibly on the bankruptcy laws; and although his creditors accepted a composition, he afterwards honourably paid them in full, a fact attested by independent and not very friendly witnesses. Subsequently, he undertook first the secretaryship and then the management and chief ownership of some tile-works at Tilbury, but here also he was unfortunate, and his imprisonment in 1703 brought the works to a standstill, and he lost £3000. From this time forward we hear of no settled business in which he engaged.