A posteriori – definition and meaning

A posteriori is a judgment or conclusion based on experience – based on watching things happen – or being told by others about their experiences. For example, the Sun has set and risen every day since I was born, my a posteriori knowledge – conclusions I have from observing things I have experienced – tells me that tomorrow the Sun will rise in the morning and set in the evening.

The term contrasts with a priori, which is knowledge gained through the apprehension of pure reason, intuition, or innate ideas. I know that 2+2=4 because of pure reasoning – a priori knowledge – and not because I have seen it happen so I assume it will happen again.

According to Dictionary.com, a posteriori is:

1. From particular instances to a general principle or law; based upon actual observation or upon experimental data: ‘An a posteriori argument that derives the theory from the evidence’. 2. Not existing in the mind prior to or independent of experience.


A posteriori vs a priori‘A posteriori’ refers to knowledge that we obtain through experience or other people’s testimony (listening to others’ experiences). ‘A priori’ is knowledge obtained by analyzing concepts and using logic – independent of experience.


The Internet Encyclopedia of Philosophy, part of the University of Tennessee Martin, makes the following comment regarding the two Latin terms:

“In general terms, a proposition is knowable a priori if it is knowable independently of experience, while a proposition knowable a posteriori is knowable on the basis of experience. The distinction between a priori and a posteriori knowledge thus broadly corresponds to the distinction between empirical and non-empirical knowledge.”



A posteriori – empirical

A posteriori knowledge is also known as empirical knowledge. Empirical means ‘based on, verifiable by, or concerned with observation or experience, and not theory or pure logic’.

The natural sciences are generally considered a posteriori disciplines, as are the social sciences. Social sciences include economics, politics, human geography, demography, sociology, anthropology, jurisprudence (the study and theory of law), history and linguistics.

Logic and mathematics, on the other hand, are a priori disciplines.


Imannuel Kant - a posteriori quoteImmanuel Kant (1724-1804), born in Königsberg, Prussia (now Kaliningrad, Russia), is today considered the most influential thinker of the Enlightenment era, and among the leading Western philosophers of all times. His works, especially those in the theory of knowledge (epistemology), ethics, and aesthetics, had a profound influence on later and contemporary philosophers. (Image: adapted from philosophers.co.uk)


A posteriori is a Latin term which literally translates into English as ‘from the one behind’, while a priori, also Latin, literally translates as ‘from the one before’.

Most of the empirical knowledge that ordinary people have is gained by a combination of direct personal experience and the testimony of others, i.e. listening to other individuals talking about their experiences.

More organized and complicated ways of gaining empirical knowledge are the methods used by scientists – people specialized in physics, chemistry, etc.



The statement ‘God exists’

Is the statement ‘God exists’ the result of empirical knowledge or pure logic? Philosophers will mostly say that it is a trick question, and that the answer could be argued either way.

If we propose that ‘God exists’ from design in the world, we are presenting an empirical argument, because I have to experience the design in the world to present the argument of God as the grand designer.

If I argue that ‘God exists‘ because it makes logical sense, then I am presenting an a priori analytical argument. “This is because, according to Anselm, existence is a logical necessity for God,” says an article in Philosophyzer.wordpress.com.

Video – A priory/posteriori

This Philosophy Tube video explains what ‘a priori’ and ‘a posteriori’ mean. The former is obtained by analyzing concepts independent of experience, while the latter is obtained through experience. They are both methods for obtaining knowledge.