A Priori or A Posteriori (and no that's not a butt joke)?

I figured philosophy essays counted as stuff I wrote too so I thought I may as well post it here in case anyone is interested, we actually are encouraged to write as if we were explaining to a child (the idea being that children will always ask why and it shouldn't be assumed that the reader already knows anything about the topic) so if I did well this should be comprehensible for most people, especially English language students. Anyway, here it is copy-pasted directly from my computer:

A Priori and A Posteriori                 Isaac Hampson

To understand the differences between a Priori and a Posteriori knowledge we must first understand what each of these means. A priori most literally means 'from the earlier', but here in this philosophical context means 'before experience'. This is information that can be known without actually having experienced it, hence 'before experience'. A posteriori literally means 'from the later' but in this context has the meaning of 'after experience'. This is information we cannot truly know until we have experienced it.

Assuming you know the correct application and meaning of the word 'square' you would know that all squares have four sides of equal length, a priori. You know this because if the square had three or five sides, it would be a triangle or pentagon and if the sides were not of equal length it would be a rhombus, trapezium or any other four sided shape that is not a square. By very definition, a square must be square. It is necessary that all squares are square-shaped. Similarly, a widow is defined as a female whose husband has perished. A woman who has never married can therefore not be a widow, if she had no husband to begin with. Also, a wife whose husband still lives and has no dead ex-husbands cannot be a widow. Only a woman who fits the exact criteria of a widow can be called widowed.

On the other hand one might say an egg tastes like an egg. This is not necessarily true. While a large number of eggs do taste like eggs, some contain embryos and thus taste like embryo, others are rotten and therefore taste rotten. The only way to truly know precisely what an egg tastes like is to taste it yourself. Even if someone else has tasted the egg and tells you it tastes as it should, all you know is that the other person believes it to taste like it should. If you then taste the egg also, you may find that it does in fact taste like an egg, or you may find that your opinion on the egg differs to that of your peer. Relating it back to the widow, one can say a Priori that she had a husband, who is now dead. You can say this without doubt before even getting out of bed in the morning. However, to say that she was upset about the death of her husband would require you to not only get out of bed, but also then go and find the widow and experience for yourself whether she is unhappy or not (perhaps by asking her). Before having experienced her answer you cannot know if she is unhappy or not, that is knowledge that can only be ascertained a Posteriori.

By looking at the above examples we can begin to understand the key differences between a priori knowledge and a posteriori knowledge. The first and most obvious difference is that in order for something to be known a priori, it must be true by definition or else be disqualified from it's classification (a square that is not a square is not a square), whereas a posteriori knowledge is variable and therefore impossible to accurately predict 100% of the time. (a rotten egg would outwardly appear to be the same as any egg, only once experiments have been performed can the nature of the egg be discerned). Simply put, a priori knowledge is necessarily true, a posteriori knowledge is not always true but not always false.

The second difference is that a priori knowledge can be verified by reason (and language) by the human consciousness a priori. As long as the meaning or criteria are clear, one can deduce with certainty some truths or falsities. A posteriori knowledge require proof, empirical experience based on current experience and not on memory, logic or expectation.

Conclusively, by their very definition all a priori knowledge can be known a priori, and all a posteriori knowledge can be known a posteriori. Usually, it is our brain that comprehends a priori knowledge with help from the senses, and our senses that relay a posteriori knowledge to the brain.