Plato’s first argument

Posted: November 28th, 2013

Plato’s First Argument












Plato’s First Argument

            In the realms of philosophy and logic, an argument is perceived as an attempt to persuade an individual about a certain idea by supporting it with evidence or reasons for acceptance or plausibility. Not or arguments are valid. The validity of an argument does not necessarily depend on the actual truth or falsity of the underlying premises or conclusion. The validity of the argument depends on whether it has a valid logical form. The soundness of an argument is based on whether it is valid, has a true premise and a true conclusion. Plato and Descartes are acclaimed philosophers of age who during their time forwarded many arguments. One is Plato’s First Argument for the Immortality of the Soul; argument from opposites and Descartes’ “cogito ergo sum”; argument that he knows that he exists (Beardon, 2000).

On Plato’s first argument for the Immortality of the Soul; argument from opposites, the philosopher’s main argument is that souls are immortal. In support of this argument, Plato says that the living derives its existence from the dead and therefore souls exist even in death. If any substance results into a certain property, then the substance results from the property from being the opposite to being the property. With this regard, the property of being alive has an opposite in death. The implied premise from above is that everything that is alive has come to be in that state. With this regard being alive derives its state from being dead (Barnet, & Bedau, 2011).

The argument is therefore valid but its soundness is somewhat debatable. The first premise is founded on a form of truism in that a substance cannot become a given property if it existed as that property. The philosopher therefore assumes that the standard does not take into account all form of becoming a certain property other than through the development from an already existing but non-property item.

In essence we find that there are two kinds of opposites. There are those that are contrary in that no item can take both properties although there are those that may take up neither such as being red or blue and contradictory opposites where all items must take up only one aspect such as the case of being square and not being square. This argument is not necessarily sound because there are objects such as stones that are considered as not having a life. With this regard, the argument fails in terms of movement to the final conclusion with it being invalid. The conclusion that the soul exists in Hades is non-sequitur; it does not follow. The conclusion can only be attuned when the soul is non-existent. The argument fails in showing that anything lives or dies more than once. The philosopher seems base his idea on the customary sense of death (meaning that the item already lived) when in the true sense the argument can only be termed as sound when dead means not-living. In this case, the conclusion then is non-sequitur (Brandon, & University of the West Indies, 1999).

Descartes’ “cogito ergo sum”; is an argument that he knows that he exists. The conclusion of the argument is “I know I exist.” The explicit premises derived from the argument is that if one believes that he exists, and then he exists. The argument has three implicit premises with one if there is not basis of doubting p, then p is assured of. Second, if one is sure of p, then one has knowledge of p. thirdly, if there is basis of uncertainty for the belief in p, then there arises a situation where there is the belief in p, but p is not true.

The validity and soundness of the argument can be proved by reductio ad absurdum. By considering an assumption A, where there is basis for doubt on ones belief that he exists, then according to the third implicit premise, then there are two possibilities of one believing on his existence and two not believing on his existence. This scenario can be taken as IC1. However, the first premise states that if one believes in his existence, then he does exist. With this regard, according to the first premise, there can never be an instance where one believes that he exists but then fails to exist. This scenario can be taken as IC2.

The two, IC1 and IC2, seem to contradict one another. By reduction, we find that assumption A is not true. This can be taken as IC3. Since assumption A is false, then in conformity to IC3, there can never be a basis of doubt that I exist. This being the case, substituting into the first implicit premise and IC3, we find that through modus ponens, that one can be sure of his existence. This can be termed as IC4. Therefore, by executing a substitution into the second implicit premise and IC4, we find that through modus ponens, the conclusion is true that “I know I exist.”

From the analysis, it is evident that the argument is valid since the structure comprises of exclusive valid moves. This is as proven by the reductio ad absurdum. The first premise is in itself unobjectionable: if one believes anything, then he or she must be in existence. The philosopher makes quite clear that this does not necessarily mean that the body or brain is in existence. The third implicit premise indicates a basis for doubt. The second implicit premise is questionable on the other hand. Certainty may not be a necessity for knowledge since there could be instances where one may be sure of something and yet be wrong. This being the case, the person may not necessarily have the knowledge, although the person thought he did. The philosopher does not want the basis of his conclusion being simply that he thinks he knows he exists (Lunsford, Ruszkiewicz, & Walters, 2010).

The first implicit premise can also be put into question. This is in the case where there exists some belief whereby there is not basis of doubt in addition to there being no positive reason to believe. The fact that there fails to be a basis of doubt does not necessarily imply that there lies sufficient reason to believe. This can be rendered as the fallacy of “appeal to ignorance.” If the philosopher is just attempting to give proof of his existence, then the argument alludes to the question since it presumes that the questioner is in existence. However, the premises are all conditional statements. With this regard, there is no premise on its own that presupposes the existence of the “I”. In addition, the conclusion does not simply state that “I exist;” rather “I know that I exist.”   This argument can therefore be termed as the better argument in terms of soundness since it has a true premise and a true conclusion.



Barnet, S., & Bedau, H. A. (2011). Current issues and enduring questions: A guide to critical thinking and argument, with readings. Boston: Bedford/St Martin’s.

Beardon, A. F. (2000). Complex analysis: The argument principle in analysis and topology. Chichester [Eng.: Wiley.

Brandon, E., & University of the West Indies (Mona, Jamaica). (1999). Argument analysis. Mona: U.W.I. Mona.

Lunsford, A. A., Ruszkiewicz, J. J., & Walters, K. (2010). Everything’s an argument: With readings. Boston: Bedford/St. Martins.





Expert paper writers are just a few clicks away

Place an order in 3 easy steps. Takes less than 5 mins.

Calculate the price of your order

You will get a personal manager and a discount.
We'll send you the first draft for approval by at
Total price:
Verified by MonsterInsights