The following list contains some of the more important and frequently used Latin terms and phrases employed in the philosophical writings of
the Scholastic philosophers and modern thinkers up to the 18th century when Latin was no longer used as the universal language of scholarship.
This list is by no means meant to be complete. I will keep adding new terms and phrases to it as I encounter them in my readings.
1. Basic Principles of Philosophy
idem nequit simul esse et non esse sub eodem respect
nothing can be and not be at the same time and in the same respect (aka as the principle of contradiction)
principium contradictionis
principle of contradiction
ens est quod est
a thing is what it is, everything is identical with itself (aka as the principle of identity)
principium identitatis
principle of identity
ens aut est aut not est
a thing is or is not, there is no middle ground between being and non-being (aka as the principle of the excluded middle)
principium exclusi medii inter duo contradictoria
principle of excluded middle
quidquid est, habet rationem sui sufficientem
whatever is, has a sufficient reason for its being (aka as the principle of sufficient reason)
principium rationis sufficientis
principle of sufficient reason
nihil est sine rationale cur posit sit quam no sit
nothing is without a reason why it is rather than is not (the principle of sufficient reason as defined by Christian Wolff)
entia non sunt multiplicanda sine ratione
one must not assume more or higher causes than are necessary for an adequate explanation (the famous Ockham's razor, a principle still used in science today)
frustra fit per plura quod fieri potest per pauciora
It is futile to do with more things that which can be done with fewer (Ockham)
nihil est in intellectu quod non fuerit in sensu, nisi ipse intellectus
nothing is in the intellect which has not been in the sense except the intellect itself (Leibniz added 'nisi ipse intellectus' to this empiricist principle)
omne ens est verum, omne unum est ens
every being is one, whatever is one is being (the Scholastic theory of being, being and unity are convertible: ens et unum convertuntur)
principium identitas indiscernibilium
the principle of the identity of indiscernible things (Leibniz's principle that two things, which are not distinguishable, are identical)
omnis determination est negatio
every determination is a negation
2. Special Scholastic Principles and Terms
natura nihil facit frustra
nature does or makes nothing in vain or uselessly or to no purpose
ex nihilo nihil fit et nihilum nihil potest reverti
out of nothing nothing is produced and nothing can become nothing again
nihil cognoscitur nisi secundum quod est actu
nothing is known except so far as it is actual (a guiding principle of Thomas Aquinas. For example, it is by seeing what people do that you discover what they can do)
forma dat esse rei
form gives being to the thing or the essence of a thing is its form (Kant's famous slogan which implies that the forms of the understanding determine the very essence of perception itself)
praedicatum inest subjecto
the concept of the predicate of a true proposition is always contained in that of the subject (A scholastic principle adopted also by Leibniz for this theory of truth and substance)
operari sequitur esse
acting follows being, that is, what we do follows from what we are (existence is the first act of a real being, action its second act)
fides quarens intellectum
faith seeking understanding (guiding principle of St. Augustine and St. Anselm, meaning that when Christian revelation is accepted in faith, human reason then sets out
to understand the truths of faith)
lumen rationis (also: intellectus principiorum, intellectus agens)
the power of the mind to know universal principles common to all knowledge
simplex veri indicium
simplicity is a sign of truth
nihil fit sine causa
nothing happens without an efficient cause
universale ante rem
universals as ideas in the mind of God, Plato's Ideas
universale in re
universals as the essence of a thing
universale post rem
universals as abstract general concepts (genus, species) in our mind
in mundo non datur hiatus, non datur saltus, non datur casus, not datur fatum
in the [sensible] world there is no leap, no gap, no chance, no fate (aka as the law of continuity)
creatio ex nihilo
creation out of non-being/nothing
adaequatio intellectus et rei
conformity of intellect/understanding/mind and thing
genus proximum et differentia specifica
genus and the specific difference (elements of a definition according to Aristotle, for example: human being = rational animal. 'Animal'
is the genus to which a human being belongs and 'rational' is what differentiates the human species from another animal species)
eadem est scientia oppositorum
affirmations and their corresponding negations are one and the same knowledge (an Aristotelian slogan. For example, health may be incompatible with sickness, but knowledge of health is compatible with knowledge of sickness,
is actually the very same thing)
omne quod movetur ab alio movetur
everything that moves is moved by something else (principle of the theory of motion and causation of St. Thomas Aquinas)
3. Philosophical Terms
a priori
from the former (presupposed, opposite of a posteriori)
a posteriori
from the latter (based on experience or observation, opposite of a priori)
cogitabile
thinkable, conceivable, imaginable
dabile
given in perception, as representation
terminus ad quem
goal, object, purpose, end
terminus a quo
point of origin, beginning, starting point
liberum arbitrium indifferentiae
free choice of indifference, free choice of the will
ens rationis
logical being, entity of reason, conceptual entity, abstract logical entity having usually no positive existence outside the mind
ens reale
real being, an entity that has either actual or potential existence beyond the confines of the finite mind
ratio essendi
cause or ground of the existence of a thing
intuitio intellectualis
intellectual intuition
haecceitas
haecceity, individual difference, thisness, principle of individuation
principium fiendi
principle of becoming
principium essendi
principle of being or existence
principium cognoscendi
principle of knowledge
sub specie aeternitatis
from eternity’s point of view (see Spinoza: Ethics)
4. Logical Terms
post hoc, ergo propter hoc
after this, therefore because of this (a logical fallacy where one assumes that one thing happening after another thing means that the
first thing caused the second)
deductio ad absurdum
absurdity in deduction/conclusion
reductio ad absurdum
leading back to the absurd (proves the thesis of an argument by showing that its opposite is absurd or logically untenable)
reductio ad infinitum
leading back to the infinite (an argument that creates an infinite series of causes that does not seem to have a beginning)
quod erat demonstrandum (q.e.d.)
what was to be demonstrated
tertium non datur
a third is not given (a logical axiom that a claim is either true or false, with no third option)
tu quoque
you too (the logical fallacy of attempting to defend one's position merely by pointing out the same weakness in one's opponent)
petitio principii
begging the question (a logical fallacy in which a proposition to be proved is implicitly or explicitly assumed in one of the premises)
contradictio in adjecto
a contradiction where the adjective contradicts its noun (e.g. square triangle)
dictum de Omni et Nullo
the maxim of all and none (in Aristotelian logic, this is the principle that whatever is affirmed or denied of a whole kind K may be
affirmed or denied (respectively) of any subkind of K. This principle is fundamental to syllogistic logic in the sense that all valid syllogistic
argument forms are reducible to applications of the two constituent principles dictum de omni and dictum de nullo)