> **OP:** Given without knowledge one can only speculate, does Buddhism suggest one should delay certain questions until one can empirically
> get a definite answer?
> 
> **OP:** For example, the jhanas are not immediately accessible, and thinking about them might lead to speculation. What is speculation in
> Buddhism? Should one always restrict their attention and cognition to
> what is immediately accessible?

The Buddha certainly valued pragmatism and discouraged metaphysical speculation.

Does this mean that ALL speculation is discouraged?

The answer to this is NO. Only speculation that is not useful towards the ending of suffering is discouraged.

For e.g. when did samsara first begin? How did the universe originate? What's the range of the Buddha's abilities? How do the consequences of karma work precisely? You can find some of these in [Acintita Sutta][1] and also the [Parable of the Poisoned Arrow][2]. Speculation on topics like these were strongly discouraged.

As for topics that are useful towards the ending of suffering, speculation is not discouraged. Without investigation, contemplation, reflection and speculation, it's impossible for a learner to learn and understand new things. **Correcting your mistaken speculations is a great learning method.**

Also, in the suttas, asking difficult questions based on speculative thinking was not just allowed by the Buddha but also used by him as a tool to convey teachings.

For example, from [SN 12.46][3]:

> As he was sitting there he said to the Blessed One: "What now, Master
> Gotama: Is the one who acts the same one who experiences [the results
> of the act]?"
> 
> [The Buddha:] "[To say,] 'The one who acts is the same one who
> experiences,' is one extreme."
> 
> [The brahman:] "Then, Master Gotama, is the one who acts someone other
> than the one who experiences?"
> 
> [The Buddha:] "[To say,] 'The one who acts is someone other than the
> one who experiences,' is the second extreme. Avoiding both of these
> extremes, the Tathagata teaches the Dhamma by means of the middle:
> *(explains dependent origination)*
> 
> When this was said, the brahman said to the Blessed One: "Magnificent,
> Master Gotama! Magnificent! Just as if he were to place upright what
> was overturned, to reveal what was hidden, to point out the way to one
> who was lost, or to carry a lamp into the dark so that those with eyes
> could see forms, in the same way has Master Gotama — through many
> lines of reasoning — made the Dhamma clear. I go to Master Gotama for
> refuge, to the Dhamma, & to the community of monks. May Master Gotama
> remember me as a lay follower who has gone for refuge from this day
> forward, for life."

And there are many more such examples in the suttas. In the [Attakari Sutta][4], we find someone speculating that there is no self-doer and he was corrected by the Buddha.

Of course, one also needs to practise the teachings (through the [Noble Eightfold Path][5]) and not just contemplate it. But, investigation, contemplation, reflection and speculation forms part of the journey of learning the Dhamma, in order to foster [Right View][6], which is the forerunner of the path.

> **OP:** I guess I could also add: How does one know when one is speculating?

If you have [doubt (*vicikiccha*)][7] in your mind, then you're most likely speculating about the Dhamma. The explanation of doubt in Buddhism from this Wikipedia page is:

> The reality of vicikicchā is not the same as what we mean by doubt in
> conventional language. Vicikicchā is not doubt about someone's name or
> about the weather. Vicikicchā is doubt about realities, about nāma and
> rūpa, about cause and result, about the four noble Truths, about the
> “Dependent Origination”.

Another sign of mistaken speculation is that it may lead you towards the [three poisons][8] of lust/ greed, aversion and delusion. A good example of this is the [Vesali Sutta][9] - in which some monks who misunderstood the Dhamma committed suicide.


  [1]: https://www.accesstoinsight.org/tipitaka/an/an04/an04.077.than.html
  [2]: https://en.wikipedia.org/wiki/Parable_of_the_Poisoned_Arrow
  [3]: https://www.accesstoinsight.org/tipitaka/sn/sn12/sn12.046.than.html
  [4]: https://www.accesstoinsight.org/tipitaka/an/an06/an06.038.niza.html
  [5]: https://www.accesstoinsight.org/lib/authors/bodhi/waytoend.html
  [6]: https://www.accesstoinsight.org/ptf/dhamma/sacca/sacca4/samma-ditthi/index.html
  [7]: https://en.wikipedia.org/wiki/Vicikitsa
  [8]: https://buddhism.stackexchange.com/q/26544/471
  [9]: https://www.accesstoinsight.org/tipitaka/sn/sn54/sn54.009.than.html