Epistemic Modality or Do I HAVE to read this?

Don't worry, that's just one of those lovely linguistic terms that you get when you look up modal verbs.

Expressions of obligation and necessity tend to be tricky in any language, so you will be glad to hear that Gaelic is no different! And before we start, I would like you to think about the many ways in which we can express necessity to do something in English: must, have to, be compelled, be forced, be obliged, be required, got to, ought, should ... all those words we hated as children.

So how is Gaelic tricky? Well, because it has about 5 basic expressions which can all be translated as "must" into English. However, they aren't all the same; some differ slightly in meaning, some in focus, and some in use. These basic expressions are (here, all are given in the 1st person singular): feumaidh mi, bidh agam ri, thig orm, 's fheudar dhomh and 's éiginn dhomh.

Above, you can see we've already encountered our first hurdle which is the tense to give them. As we will see, you can't use them indiscriminately in just any tense.

For a change, you'll get the solution first and the explanations afterwards:

feumaidh mi	bidh agam ri	thig orm	's fheudar dhomh	's éiginn dhomh
1 I will require 2 It is necessary for me, I must	I will have to (more obligation than feumaidh)	I will have to (focus on external pressure)	It is necessary for me, I must	I really must (strong compulsion)

So what's the catch?

Let's start with feumaidh. This word, which interestingly comes from the Old Irish word feidm "need, use" has two basic meanings and/or usages. One meaning is that something is required, for example, feumaidh mi airgead (a chum na siùrsaich a phàigheadh) "I need money (to pay the hooker)". In a way, this is the "original" use of the word and is close to the modern Irish usage, for example, tá mé i bhfeidhm gabhair "I am in need of a goat" (don't ask). Later, this word extended its meaning to include "must, have to" in Gaelic. For example, feumaidh mi an t-siùrsach a phàigheadh "I have to pay the hooker".

Tragically, it's one of our defective verbs (which means it's a verb which does not have forms for all the tenses) so we'd be a bit stuck if this was the only verb meaning "must".

Notice (we'll talk a bit more about this later) that this verb is strictly a future form: feumaidh mi, a dh'fheumas mi, chan fheum mi ... so there is a distinct flavour of things which are yet to happen, or can happen yet, attached to this verb (yes, there are conditional forms too but we'll get to that later).

Note also that in comparison to 's fheudar dhomh and tha agam ri, feumaidh has a slightly more intentional flavour. Compare feumaidh mi an leabhar seo a leughadh "I have to read this book (because I heard it's really good)" with tha agam ris an leabhar seo a leughadh "I have to read this book (because I have to write an essay on it by tomorrow)".

In comes Old Irish fétir. Originally, this meant "possible", and it still does in Irish. For example, is féidir liom ranníocaíochtaí deonacha a íoc means "I can pay voluntary contributions". In Gaelic though, this word has undergone a partial shift to supply past and present tense forms, for example, feumaidh, which tends to be present/future, and b' fheudar dhomh an t-siùrsaich a phàigheadh, for past, "I had to pay the hooker". Without the convenience of b' fheudar, that sentence would have to be expressed in roundabout way using bha feum agam air airgead a chum na siùrsaich a phàigheadh ... "I needed money to pay the hooker". Sooo ... 's fheudar and b' fheudar mean pretty much the same thing as feumaidh, in the sense of "must", except sentences with 's fheudar and b' fheudar have a present/past focus.

Confusingly though, this verb retains its original meaning in a number of expressions and usages, especially with negatives: rud nach b' fheudar "a thing that wasn't possible"; chan fheudar nach dig mi "I will certainly come (=It's not possible for me not to come)".

Next in line is bidh agam ri. This is perhaps the most straightforward of all the "must" expressions as it expresses an obligation of "must" that's plain, simple, and available in every tense ie bidh agam ri, tha agam ri, bha agam ri, bhiodh agam ri ... Tha agam ri siùrsach a phàigheadh "I have to pay a hooker".

Thig orm is interesting because it also gets translated as "have to, must" but has a different focus. With the others, the focus can be either internal or external, but with thàinig orm an leabhar seo a leughadh "I had to read this book" there's a strong element of some external factor making you read it. It's perhaps better translated as "I was compelled to read the book".

The last one is quite similar but simply with more urgency: b' éiginn dhomh falbh oir bha mo thaigh air theine "I had to (was forced) to leave because my house was on fire". Considering that éiginn means something between distress and necessity, that is not really surprising. There's also the expression 's éiginn dhomh "I am forced to".

Here's a full paradigm of feum:

Future	Relative Future	Dependent Future
feumaidh mi	a dh'fheumas mi	am feum mi? nach fheum mi? chan fheum mi
I have to	that I would have to	will I have to? etc.
Conditional		Conditional Dependant
dh'fheumainn dh'fheumadh tu ... dh'fheumamaid dh'fheumadh sibh ...		am feumainn? (nach fheumainn?) am feumadh tu? (nach fheumadh tu?) ... am feumamaid? (nach fheumamaid?) am feumadh sibh? (nach fheumadh sibh?) ...
I would need to/had to; etc		would I need to/have to? etc
Impersonal Forms Future
feumar		am feumar? nach fheumar? chan fheumar
it must be		must it be? etc
Past
dh'fheumtadh		am feumtadh? etc
it had to be		did it have to be?

And note, that although a root form feum exists, this is not used for issuing commands, rather feumaidh is used, for example, feumaidh tu seo a dhèanamh "you must do this".

Beyond these expressions there are some more, as in English, but not with the basic meaning of "have to, must" (the list is not exhaustive):

an eisimeil	obliged to
tha e an eisimeil mo chuideachadh	he is obliged to help me
mar fhiachaibh air	required to
tha e mar fhiachaibh air mo chuideachadh	he is required to help me