_Disputationes Tusculanae_, treating of certain conditions essential to
morality and happiness;

_De Natura Deorum_, an examination of the principal theories regarding the
nature and power of the gods;

_Cato Maior_, on old age; _Laelius_, on friendship;

_De Fato_, discussing Fate and Free Will;

_Paradoxa_, a book setting forth certain remarkable views of the Stoics;

_De Officiis_, a treatise on practical ethics, the application of moral
principles to the questions and difficulties of ordinary life.

These works, written mostly in 45 and 44, are, except the _De Cons.,_ still
extant. To the list may be added also other works of a rhetorical nature,
such as the _Topica_ and _De Optima Genere Dicendi_, and some lost
philosophical books, such as _De Gloria_.

Even though allowance be made for the fact that Cicero was giving in Latin
the substance of Greek books with which he had been familiar from boyhood,
the mental vigor and literary power exhibited by this series of works
appear prodigious when we consider their great compass and variety and the
generally high finish of their style.

_References._--For a fuller account of Cicero's philosophical views and
writings consult Ritter, 'History of Ancient Philosophy', Vol. 4, Ch. 2;
Maurice, 'Moral and Metaphysical Philosophy', Ch. 7, § 5; Tennemann and
Morell, 'History of Philosophy', Ch. 3; Ueberweg, 'History of Philosophy',