When I said that “releasing the parking brake is necessary to move the car”, it was assumed that the parking brake was activated. In most cases, however, there is no need to release the brake because the brake has not been activated at all. I do not need to specify the necessary condition. If memory is an ability to trace our own past experiences and witnesses, then a necessary condition for Penelope to remember giving a lecture that it took place in the past. On the other hand, it is enough for Penelope to remember the lecture now to conclude that it was given in the past. In a well-known attempt to use the terminology of necessary and sufficient conditions to shed light on what it means that one thing is the cause of another, J. L. Mackie suggests that the causes are at least INUS conditions, that is, “insufficient but necessary parts of a condition that is itself useless but sufficient” for its effects (Mackie, 1965). A pattern such as Mackie`s became the basis of the “sufficient cause model” of disease in epidemiology (see Rothman 1976) and continues to influence medical thinking about the causes of disease as well as definitions of causality in psychology and law (VanderWeele 2017).
It is also possible – according to standard theory – to use “only if” to identify a necessary condition: it can be said that Jonah was swallowed by a whale only if it was swallowed by a mammal, because if a creature is not a mammal, it is not a whale. The equivalent of (i) above for this reason is the phrase “I only opened the door when I used the key” – a perfectly natural way of emphasizing that using the key was necessary to open the door. Another example would be that microwave water is a sufficient condition for heating water, but it is not a necessary condition because there are other ways to heat water that do not involve microwaves. A sufficient condition fully explains how a particular result could have occurred, without being the only possible explanation of how that result could have occurred. In general, a necessary condition is one that must be present for another condition to occur, while a sufficient condition is one that produces said condition.  The statement that one statement is a “necessary and sufficient” condition of another means that the first statement is true if and only if the second is true. That is, both statements must be true or false at the same time.    This is where ceteris paribus gets tricky. Very often, the assumption “all other things are equal” does not strictly mean “all other things”, but rather a subset of other things and above all (and important) the conditions necessary for the effect.
As you can imagine, it is very easy to get entangled in a jumble of necessary and sufficient conditions because the logic of conditions is so closely intertwined. This is especially the case when you`re trying to determine if one thing will cause another. As mentioned at the beginning of the article, the specification of necessary and sufficient conditions is traditionally part of the philosophical activity of analyzing concepts, concepts and phenomena. Philosophical research on knowledge, truth, causality, consciousness, memory, justice, altruism, and a host of other questions is not intended to state evidence or explanatory relationships, but to identify and develop conceptual relationships (see Jackson 1998 for a detailed presentation of conceptual analysis and the additional entry on analytical concepts in analytic philosophy for an overview). But again, the temptation to look for reasons for this or reasons to think is not far away. While conceptual analysis, like dictionary definition, avoids conditions of proof and explanation, conditions of proof seem to be natural consequences of definition and analysis. That Nellie is an elephant may not be (or the) reason she is an animal, any more than a figure is a square, a reason why she has four sides. But some claims seem to make sense even in such contexts: being an elephant apparently gives reason to think that Nellie is an animal, and a particular character can be considered to have four sides because it is a square, in a conclusive sense of “because”. The idea of sufficient condition is that it is enough to make things happen.
For example, in most cases, it is enough to press the gas to move the car forward. That is not the only thing he would do; For example, you can move the car forward by pushing it. So what is a necessary (or sufficient) condition? This article describes the difficulties in fully answering this question. While the concept of sufficient condition can be used to define what is a necessary condition (and vice versa), there does not seem to be an easy way to give a complete and unambiguous account of the meaning of the term “necessary (or sufficient) condition” itself. If something is a necessary condition, it means that it must necessarily take place for a certain result to occur; The result cannot occur without this condition being met. To attend a specific concert, you need tickets. Therefore, the possession of tickets is a necessary condition to attend this concert. The statement that Q is necessary for P is colloquially equivalent to “P cannot be true unless Q is true” or “if Q is false, then P is false”.   On the other hand, it is the same as “whenever P is true, Q is also true”.
The discussion of “necessary and sufficient conditions” is well understood in philosophy, and that is why I sometimes make the mistake of assuming that it is generally understood in the wider community. This article addresses this by describing the concept and why it is important. Why is this important? Because it probably points to the most common mistake that concerns conditions: insufficient funds that are not needed. Given the different roles of the newly identified “if”, it is hardly surprising that generalizations about necessary and/or sufficient conditions are difficult to formulate. For example, suppose someone tries to formulate a sufficient condition for a seminar to be good, in a context where the speaker and all listeners share the opinion that Solange`s presence is a reason why seminars would be good. In this case, one could say that Solange`s presence is a sufficient condition for the seminar to be good in the sense that their presence is a reason why it is good. Is there a similar sense in which the goodness of the seminary is a necessary condition for Solange`s presence? The negative answer to this question is already clear from the previous discussion. If we follow Wright`s suggestion mentioned above, we get the following result: that the seminar is not good is a sufficient condition for Solange not to be present.
But this cannot plausibly be read as a sufficient condition in the sense of a reason for it. At most, the fact that the seminar was not good could be a reason to believe that Solange was not there. So, in general, how can we determine what kind of condition is expressed in an “if” sentence? As mentioned in the case of the naval battle, if formal paraphrasing captures the meaning of what is being said, and if the phrases “if p, q” and “p only if q” seem idiomatically equivalent, then a conclusive interpretation is in order, Wright equivalences will apply, and the material condition gives a reasonable account of these cases. As noted above, such an approach has limitations and provides, at best, a partial account of the circumstances in which conditional judgments express necessary or sufficient conditions. Let us now consider a sufficient condition. Throwing a football into the net is enough to score a goal, as a goal is defined by the ball crossing the goal line and entering the net via a legal touch. According to this definition, the necessary condition for a goal is that the ball crosses the goal line. However, kicking the ball into the net is not necessary to score a goal, as you can also use your head towards the goal. If P is sufficient for Q, then knowing that P is true is reason enough to conclude that Q is true; However, knowing that P is false does not satisfy the minimum need to conclude that Q is false. The front door is locked.
To open it normally and enter the house, I must first use my key. Thus, a necessary condition for opening the door without strength is to use the key. It therefore seems true that these strange results do not occur in some non-classical logics, where it is required that the premises be relevant to the conclusions drawn from them, and that the precursors of real conditions are also relevant to the consequences. But even in versions of relevance logic that avoid some of these strange outcomes, it`s hard to avoid all the so-called “implication paradoxes” (see the entry on conditional logic and relevance logic). For example, a contradiction (a statement of the form “p and not p”) is a sufficient condition for the veracity of a statement, unless the semantics of the logic in question allow the inclusion of incoherent worlds. Jermaine considered that a necessary condition of the presidency was sufficient. Yes, it is necessary for the President of the United States to be a born citizen of the country, but this is not the only qualification. Another restriction is that a presidential candidate must be at least 35 years old.
Unfortunately, Jermaine is still in high school, so his birthplace alone is not enough to run for president. But conditions don`t have to be causes. The granting of an authorisation is another type of condition. For example, a driver`s license gives you permission to drive.