Detailed example:
Synthesis is a complicated concept and so it is worth working though a more detailed example.
In the context of Wikipedia, careless use of the rules can lead to some unusual statements being claimed based on referenced sources. Often this might come about due to the editing process itself, where people seek to find citations that back up writing.
Synthesis recognises that although information apparently can be carefully sourced, if the actual detail of a statement is not properly referenced, flawed logic can result in unsupportable claims. Whilst many of these simple logical deductions are harmless and need not be challenged, synthesis is not allowed where it is challenged and seeks to advance a position.
The following example made deliberately bizarre to emphasise the problem closely follows a real life example, though the concepts of the real problem might not be quite as obvious at first sight. To understand the example, we need to do some scene setting so we can understand how the subtle problems of synthesis arise. It is also helpful to understand that our editor is a fervent campaigner against tinted windshields on safety grounds.
In Nirvana, there was growing concern about road safety issues related to driving but tinted windshields and sunglasses were seen as essential to coping with this land of perpetual sunshine. There were a sudden spate of deaths on pedestrian crossings and eventually a public enquiry was held into these. The so-called Blindfold Inquiry dealt in some detail with the various causes and noted that although tinted windshields and sunglasses had been raised as concerns, the actual cause of all the accidents was found to be the craze of young drivers proving that they could drive around blindfolded. There were no accidents that fell outside this cause and the Inquiry was accepted as a sound review of various research. The Inquiry came to no conclusion on tinting windshields or using sunglasses whilst driving, but there was a general public consensus that these were a problem, no viable alternatives were accepted. The Inquiry was available as a public document on the web running to 100 pages of detailed summary and assessment of various opinions. Responding to increasing public concern the President of Nirvana called for the banning of tinted windscreens and scientists also were concerned and wanted to see all devices that impaired visibility removed.
A respected news agency in Nirvana published the following release which was accepted by all as a fair high level summary of the issues.
Tinted windshields blamed for road safety disasters
The President of Nirvana called for the banning of tinted windscreens saying, "Tinted windshields are a disaster in the making, they must be banned." Scientists involved in the famous crossing disasters inquiry also demanded changes, "The Blindfold Inquiry shows that impared visibility can cause disasters." Scientists went on to say, "Sunglasses are a timebomb, they must be banned."
The Wikipedia article was written as follows:
Tinted windshields, also known as sunglasses(citation to above news release), are a harmful form of decoration for cars. Scientists have blamed sunglasses as the cause of deaths on pedestrian crossings.(citation to above news release)
Editors had originally complained that sunglasses were not the same as windshields and the Inquiry did not blame sunglasses, but the author had looked for references and found the press release from the respected news agency.
The two key problems with this synthesis is that the release never actually says that sunglasses and windshields are the same thing, it relies on an assumption that the title of the release, the President and the scientists are talking about the same thing. The writing of the release in this loose fashion does allow the casual reader to be confused. Once read in this way, this synthesis using the article definition is used in circular fashion to confirm the article from the release. The fact that the statements come from the same source is not a barrier to a false analysis of the source.
The second issue is that scientists never actually said that tinted windshields were the problem in the release, and although it is common sense that poor visibility is a related issue, the scientists did not tie the sunglasses and the blindfolding together in the release, there is no quote that actually ties the two statements together. There is nothing incorrect or misleading in the press release, the quotes are accurate, but the summary loses the context of the statements.
The Inquiry had wording in it that clearly defined the problem yet policy is used to dismiss the high quality inquiry statement. The argument is that the press-release must be more appropriate to Wikipedia as from the perspective of the press-release the Inquiry is a primary source and does not apparently have the validity of a secondary source which has tested it. It shows the danger of assessing reliable sources incorrectly. We can also be critical of seeking to suggest that casual comments of scientists are suggested as scientific consensus. Regardless of these policy pages, editing requires that critical faculties remain engaged at all times.