Necessary vs. Sufficient Conditions
Many academic arguments must discuss aspects of a topic that are "necessary" to the topic's existence, success, solution if it is a problem, etc. Other aspects of the topic may be "sufficient" to make the topic exist, succeed, or be solved, etc. This distinction can easily be explored in the product purchase recommendation paper assigned for English 105, but it has applications in all fields of rational argument.
Necessary conditions are those which must exist in order for something to be. For instance, fire requires the presence of fuel, oxygen, and an ignition source. Take away any one of these conditions, often called "the fire triangle" by fire fighters, and fire will not occur. All three are "necessary conditions." Similarly, all of the products you take the time to examine probably will have the "necessary features" to have a chance to meet your best readers needs. The distinction between those who make the "first cut" and those which are eliminated may well turn on whether the products' features meet those needs "sufficiently." If the products' features are sufficient to the readers' needs, the products might be good enough to recommend.
Sufficient conditions are those which are all that are required for something to exist. None of the "fire triangle" conditions is sufficient, in itself, to cause fires. However, if all three of them are present in large enough quantities, conditions may be sufficient for fire to occur. Your very best products' most necessary features also must be present and must be good enough, individually, in order for your recommendation to succeed. It might then be the case that some other condition, like price or availability or repair costs might suddenly emerge as the distinguishing feature that enables you to discriminate among the "sufficient" products to find the best one. "Sufficient causes" are crucial because they are what scholars would consider necessary to believe something is the case, like your thesis.