I am looking for a word or phrase describing a research topic that many scientists and researchers are working on, but not finding any fundamental results. For example, deep learning right now.

  • They are working hard for unobtainium. May 12, 2018 at 5:30
  • What do you mean by "fundamental results"? Deep learning has been pretty successful in image/object classification, face recognition, OCR, and even image captioning. I’d say it is getting fundamental results, so I must be misunderstanding you.
    – Pam
    May 12, 2018 at 9:47
  • @Pam I think the OP means this: 'A main criticism [of deep learning] concerns the lack of theory surrounding the methods. Learning in the most common deep architectures is implemented using well-understood gradient descent. However, the theory surrounding other algorithms, such as contrastive divergence is less clear. (e.g., Does it converge? If so, how fast? What is it approximating?) Deep learning methods are often looked at as a black box, with most confirmations done empirically, rather than theoretically.' (Wikipedia) May 12, 2018 at 13:40
  • @Pam As far as I know, deep learning indeed have many good applications in AI, pattern recognition and image captioning as you mention. But on the mathematical level, it does not seem to have already formulate some theories that could explain or instruct all those applications. For example, Newton's law of motion is one thing, explaining how one object moves.
    – Ethanabc
    May 12, 2018 at 13:45
  • Thanks @linguisticturn, and Ethanabc. Yes, I do remember incredulously thinking "this works? It’s too simple" when I first looked at the basic maths. There are a lot more application papers than there are pure theory, and about half of each theory paper is given over to the application of the theory via an experiment or two on common datasets. I think it’s just an application-driven field (what with all the industry involvement).
    – Pam
    May 12, 2018 at 19:35

2 Answers 2


Something that many people ardently desire, but that is very hard to obtain, is often called a holy grail. The phrase has been used in many contexts, including the scientific; googling for holy grail science brings up many examples.

  • I disagree. Holy grail means A thing which is eagerly pursued or sought after. Its location is a mystery, not its existence. OP want a word which describes something whose very cause of existence is still a mystery.
    – LWTBP
    May 12, 2018 at 11:37

elusive TFD

  1. Tending to elude capture, perception, comprehension,

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