Philosophy Word of the Day – A Priori and A Posteriori

These Latin terms mean literally “from what comes before” and “from what comes after.”  Both terms relate to how one acquires knowledge of the truth of a proposition.

An a priori proposition can be known to be true or false without reference to the evidence of experience, while the truth or falsity of an a posteriori proposition depends upon such evidence.

Examples of propositions commonly held to be known a priori include:

a bachelor is an unmarried male; 2 + 3 = 5; if you know something, then what you believe is true; if A is greater than B, and B is greater than C, then A is greater than C; no object can be red and green all over at the same time; the shortest distance between two points is a straight line; no object can be wholly in two different places at the same time; it is wrong to torture infants to death just for the fun of it; and it is unjust to punish an innocent person.

On the other hand, a proposition such as “some bachelors are very happy” can only be decided as true or false a posteriori – as a result of empirical investigation.

Ontological arguments for God’s existence are a priori, while an argument, for example, for Jesus’ resurrection from the dead is a posteriori.

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19 thoughts on “Philosophy Word of the Day – A Priori and A Posteriori

  1. Pingback: Philosophy Word of the Week – A Priori and A Posteriori |

  2. Marcello, it has been a good dialogue. I wish you God speed in your journey through life. Looking at your profile, you are on a good start. I would encourage you to look at Gordon Clark’s peers and their interaction with his thoughts and writing. I, too, like Clark…up to a point. Once you identify his perspective, it is easier to parse his thoughts.
    As you will find through your journey, each perspective brings implications that you must deal with: what can you accept and what can you not accept, from each one. Each has their flaws, in theological perspective or practice.
    But it is a worthwhile trip and one I’m glad to share with you.

    Peace and Blessing to you,


    • Good thoughts, guys, and a good dialogue. I can see some pros and cons with both approaches, but overall I lean a little more on the evidential side. William Lane Craig makes a nice distinction between knowing Christianity is true and showing Christianity is true. He holds that you can know Christianity is true without having to produce evidence for your belief; but if you want to show someone else that Christianity is true, you do need to give some kind of reasons or evidence. I think the apostles, and even Jesus, were all in favor of giving evidence so that others would believe–like evidence of Jesus’ miracles and His resurrection (of course, this was before the New Testament was even written, so they were just pointing to historical and verifiable facts). That knowing/showing distinction was helpful for me.
      Thanks again,

      • Hi fleance

        I hope my ideas can be undestood, It’s the first time I try to dialogue in a english blog.

        I think the christian don’t need to show the christianity is true. Romans 1:21 says all man know God exist but he suppress this truth.

        What we have to do is to preach the Word of God and the Holy Spirit will show internally, to every He want, the truth of christianity. There are not philosophic nor logical method to show to to atheist that God exist, it’s just understood by the work of God in the heart of his chosen people.

        God bless you

    • Thanks for your words Mitch

      I’m a chilean who is studing theology in Brazil in order to help the people of God in my country. I know Gordon Clark, I did read all his articles in trinity foundation. A pastor who I know here in Brazil has some of his books and always I can I read something of Clark.

      Sadly here in the seminary there is nothing of Clark. I will try to buy some of his books, I hope soon jejeje.

      God bless you

  3. Marcello,
    Additionally on the website giving theological words of the day (similar to this site) is this entry:
    (Latin fides, “faith”)

    Literally “faithism.” Fideism is the belief that faith is antithetical to reason. In Christian apologetics, fideists believe in a necessary dichotomy between rational intellectual conviction and spiritual emotional conviction. Faith, to them, is strongest in the absence of evidence. Many would critique this approach believing it misunderstands and misdefines faith as that which is believed in the absence of or in spite of the evidence, proposing that faith is that which is believed according to the evidence.

    credo quia absurdum, “I believe because it is absurd”—Tertullian

    Please understand that this is not meant for criticism, only edification/instruction. If it did offend you, please forgive me.


    • Mitch

      I think I’m so far of fideism, I don’t believe faith is irrational. I believe the Bible is the Word and show what God think, it’s more rational than anything. I don’t believe the Bible is absurd, I think it’s totally rational and logical.

      I don’t believe the “material evidence” should be the only way to know the truth as the materialistic philosophy says. Of course we have evidence, it’s the testimony of God on the Bible.

      Don’t worry, Like Chris said before, it’s a veri insightful dialogue.

      God bless you

  4. You are assuming that scripture was always present, even at creation. You may or may not have run into someone that is going to challenge you at this very point…and you’re going to be stuck.
    Yes, there was someone (using a personal human descriptive for God) and He left the testimony of reality, creation, as a signature. IF…people refuse to believe it (the natural materialists) for any number of reasons, it is not because of the lack of truth or in this case the objective reality of God observed through creation.


  5. Mitch

    When the Scripture say something this is true and real. There is someone who was in the moment of creation? No. But we believe this just because God say it. The atheists don’t be there when the Big Bang, they believe, happen however they believe it.

    Do you believe the Scripture need help to be true? It sounds very cientific but it’s not what the Bible says. The Bible says Scripture is a more sure word than any testimony of history.

    We are called to be not conformed to this world, to be not conformed to the materialists says nor their standars of truth or reality.

    Don’t be afraid of disagreement of the world, they never will always suppress the truth.

    God bless you.

  6. Marcelo, thank you for clarifying your remark…and I do understand that second language translation can be difficult.
    I would encourage you to think through this:
    Faith, without an objective reality, is easily perverted to fantasy. Your statement might look like this, in English, “Jesus has risen from the dead because there is objective historical proof (testimony of history not yet refuted) AND we have the testimony of scripture.” Starting with either statement is acceptable, because both are sensical statements. People ‘practice’ faith everyday by their trust in mechanical systems, of which they can’t explain, that deliver them or transfer information for them, and on and on. But that faith has a real objective reality.
    Now, realistically, in world that will challenges this process of knowing and faith, there might be some strong disagreement.

    Peace to you,


  7. I’m sorry if someone don’t like my first commentary, English is not my language and sometimes I can’t express what I want to do.

    I will try again.

    We can’t think that proposition “[Jesus] has risen from the dead” (Mt. 27:64) is true because we have empirical evidences. We think it’s true just because God say it.

    2 Peter 1 talks about the people who ear the voice of God when He say “This is my beloved Son, with whom I am well pleased,” but Peter say we have something more sure than that experience, “we have something more sure, the prophetic word, to which you will do well to pay attention” (1:19).

    Mure sure than our senses is the Word of God, this is the standar for true, not the empirical investigation.

    God bless you all.


  8. I thought that initial post was legitimate. I also appreciate this blog. We are to honor God with our mind, and this is a helpful website.

    Thanks and God Bless!

    • Thanks for the encouragement! You’re right, we are instructed to love God with all of our mind, and to take every thought captive. Christianity has a very rich intellectual tradition that’s included some of the greatest thinkers in history.

  9. Thank you for starting this. Please do not be discouraged by disparaging, argumentative remarks. There are a number of people who want to LEARN!

    Peace to you and yours,


    • Thanks, Mitch. I hope I’m one of those people who want to learn too. Marcelo’s question was insightful, and I hope my response makes sense.

    • Hi Marcelo,

      That’s a good question, and I actually thought about it right after I finished that post. I think a person could very well believe in Jesus’ resurrection based solely on the testimony of Scripture, and he or she would be justified in doing so. The main reason I believe in the resurrection is the gospel accounts, and because I believe those accounts are historically accurate. But even with basing your belief only on Scripture, I still think that counts as an a posteriori approach — because you still have to empirically investigate what the Bible says to reach your conclusion, which is a different type of investigation than an a priori investigation.
      Thanks for the insightful question!

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