Lesson 15
pamumoi seltadni

Lojban Tenses
temci valsi bau la lojban.


Thus far, all sentences that we have used have been expressed without
tense.  You haven't known, except by context, whether a sentence is
referring to a relationship, event, state, property, or amount which
is in the present, the past or the future.  You also haven't known
anything about either absolute or relative location.

The reason for this, as has been explained, is that this information
is optional.  Time is not inherently a part of "zutse", "blanu", or
"stizu", to give examples whose English keywords belong to different
English word types; a chair, a sitter, and a blue thing may have their
respective properties independent of time.  The same is true for
spatial aspects: "se zutse" is "a place which is sat in/at"; we will
eventually see that this 'place' may be expressed either as an
absolute location or as a relative one.

We may be using the word "tense" in a way that seems strange.  In
English and most other languages, tense refers to time.  Lojban, which
was invented after Einstein, is designed to reflect the potential
unity of space and time.  Since tense is optional in Lojban, you are
not obligated to assume Einstein's theory is true (this would be a
risky cultural bias, since Einstein's theory is unproven).  With
Lojban, however, it is now possible to express things in terms of a
unified space-time.  When talking about Lojban tense, we refer to both
space locations and time locations wherein the relationship expressed
by the bridi is true.

There are gismu that can be used to specifically express time and
space location, including:

	cabna	zvati	lamji
	balvi	stizu	darno
	purci	jibni

and various directional locators.  These all can be combined into
tanru to convey a sense of time and space.  tanru are ambiguous,
however, and it is desirable to be able to unambiguously specify the
tense at times.

The cmavo used to express simple Lojban tenses are easy to learn.  The
three gismu:

	cabna     now, at the same time
	balvi     future, later
	purci     past, earlier

describe the three time relationships we typically associate with the
three simple time tenses.

The three cmavo which express the corresponding time tenses are
derived from the first two letters of each gismu:

	ca     currently, is now, at the same time
	ba     will, later
	pu     did, previously, earlier

To specify location as a tense, we do not use the corresponding gismu
in selecting cmavo for the needed tense expressions.  Instead, we
parallel the demonstratives:

	ti	this-here	vi	here; at the same place
	zvati
	ta	that-there	va	there, near; at a close place
	jibni
	tu	that-yonder	vu	yonder, far; at a distant place
	darno


15.1
Tense-labelled sumti
temci seltcita sumti

By the end of this sublesson, we will see how both time and space
tense cmavo can be used in ways that make them seem quite
English-like.  Appearances are deceiving, however.  To receive the
advantages of optional tense, you must understand how it is optional.
The most common error for an English speaker is to specify tense when
it isn't necessary.  The second most common error is to generalize
from simple English-like forms on the assumption that other tense
expressions work like English.  They don't.

In discussing place structures, we have indicated that there are
situations where the place structure does not convey all the
information you want to communicate about a relationship.  If I say
"mi [cu] morsi", I am communicating a simple truth about life: at some
time or another, "dead" will appropriately describe me in relationship
to the rest of the universe.  If I say "mi [cu] klama", even if I
specify all of the other places, you have no idea when I am going, or
when I have gone.

In "mi [cu] dasni le creka", both time and space are elliptical; we've
left them out in the manner that Lojban speakers are wont to do for
other optional information.  You don't know when and where I wore the
shirt, or will wear it, because I haven't deemed it important enough
to express.  It is true that at sometime I wear a shirt, but this is
insufficient information to make meaningful deductions about any
circumstances involving time, environment, causality, etc.

When you want to add such information about a bridi as time and
location, you express this information as a sumti.  These additional
sumti are additional pieces of the relationship.  They are not
inherent to the relationship, but they may restrict, constrain, or
modify when the relationship is true.  We thus express such
information as "bridi galfi sumti" (bridi-modifying sumti) or, in
English, "modifier sumti", or more simply "modifiers".

You need to be able to tell a modifier from a regular sumti, or you
won't have any idea which sumti are which in the place structure.
Remembering the total flexibility that we have regarding which side of
the selbri we place the place structure sumti, as long as we keep them
in the right order, we need to be able to extend this concept to
modifier sumti.

We achieve this flexibility with what linguistics terms "case tags",
but which we will generally call "sumti tcita", or "sumti tags".  The
six operators we listed for time and space tense are "sumti tcita
cmavo".  We can restrict them further using tanru as "temci ke sumti
tcita cmavo [ke'e]" ("time interval type-of sumti-tag cmavo") and
"stuzi ke sumti tcita cmavo [ke'e]" ("location type-of sumti-tag
cmavo"), showing how tanru can be used to make arbitrarily fine
distinctions between concepts.

A sumti tag is attached to the front of the sumti; no terminator is
required or permitted.

Let us present the three time tags again, showing how they work in
their sumti tcita role.  For an example, we might wish to reference an
event; e.g. "lenu mi [cu] klama ti [kei] [ku]":

ca		ca lenu mi [cu] klama ti [kei] [ku]
		ca lenu mi klama ti

	"at the same time as ..."	"at the same time as my coming here"
	"simultaneous with ..."	"simultaneous with my coming here"
	"during ..."	"during my coming here"

ba		ba lenu mi [cu] klama ti [kei] [ku]
		ba lenu mi klama ti
	"in the future of ..."	"in the future of my coming here"
	"after ..."	"after my coming here"

pu		pu lenu mi [cu] klama ti [kei] [ku]
		pu lenu mi klama ti
	"in the past of ..."	"in the past of my coming here"
	"before ..."	"before my coming here"

We needn't restrict ourselves to event abstractions.  Time operators
can be used with time-of-day events:

ca lenu li re pimu [cu] tcika [kei] [ku]
ca lenu li re pimu tcika
("at the same time as when half-past-two is-the-time-of-day")

If the time being referenced is known, we can elliptically omit it:

ca lenu tcika [kei] [ku]
ca lenu tcika
("at the same time as when something ellipsized is-the-time-of-day")

It is also possible to define a time by relating it to a sumti that
represents an event, but with the abstracted selbri ellipsized.  In
this case, you need to infer from context what the selbri is:

ca li re pimu [ku]
ca li re pimu
("at the same time as [when] half-past-two [is-the-time-of-day]")
("at half-past-two")

An alternative to these forms, by the way, uses the name form of time-of-day:

ca la repimucac.
("at the same time as that which I call '2.5 hour' ")
("at half-past-two")

If the sumti of the event abstraction is omitted, we can sometimes
ellipsize the event marker:

ca le tcika [ku]
ca le tcika
("at the same time as the-time-of-day I have in mind")
"at that time(-of-day)", "at the time"

You have to be careful about this kind of ellipsis; like other
ellipsis, these are subject to the listener using plausibility to
figure your intent.  The next two examples will show this, among other
things:

pu lenu la djan. [cu] klama ti [kei] [ku]
pu lenu la djan. klama ti
("before the-event-of John coming here")

which can be put into the sentence:

pu lenu la djan. [cu] klama ti kei [ku] mi [cu] klama ti
pu lenu la djan. klama ti kei mi klama ti
("Before the-event-of John coming here, I come here.")

At least one of "kei" or "ku" must not be elided, or "mi" would be
taken as a sumti of the abstracted "nu" bridi in the labelled sumti.
In the second version, we have chosen "kei" as the more semantically
significant of the terminators.

As we said, the sumti can be expressed in any order.  To determine the
number of the place structure sumti, just pretend like the modifier
sumti aren't there.  The previous sentence is identical to:

mi [cu] klama ti pu lenu la djan. [cu] klama ti [kei] [ku]
mi klama ti pu lenu la djan. klama ti
("I come here before the-event-of John coming here.")

or:

mi [cu] klama pu lenu la djan. [cu] klama ti [kei] ku ti
mi klama pu lenu la djan. klama ti ku ti
("I come, before the-event-of John coming here, to here.")

or:

mi pu lenu la djan. [cu] klama ti [kei] [ku] [cu] klama ti
mi pu lenu la djan. klama ti cu klama ti
("I, before the-event-of John coming here, come here.")

We have left an optionally elidable "cu" in the last sentence to make
it easier for a listener to determine the main selbri.  It isn't
really needed.

The results of using a sumti other than an event abstraction after a
tense sumti tag can be very surprising:

pu la djan. mi [cu] klama ti
pu la djan. mi klama ti

does not mean the same as the previous examples.  Instead, John is
implicitly made into an event!  One plausible interpretation is that
the speaker came here before John even existed.  Lojban does provide a
means, not explained in this textbook, for saying the equivalent of "I
came here before John", meaning "I came before John did something or
other (presumably, he came)" But it is always safe to use an explicit
event.


15.2
Ellipsis of the labelled sumti
seltcita sumti nalnunsku

We can carry ellipsis another step.  After all, we can ellipsize some
or all of the other sumti from a bridi, leaving only a bare selbri -
or perhaps an incomplete one, like in the last few examples.  What if
we want to specify a time relationship to an obvious time, without
repeating it.  In this case, we leave only the tag to indicate that
the relationship is being modified significantly, and replace the
modifier sumti with an elidable "ku".  (This is a second and
grammatically distinct use of "ku".)  Thus we have "pu zo'e", or
equivalently "pu [ku]"

The result can still be expressed in the same three forms:

pu ku mi [cu] klama ti
pu ku mi klama ti
("Before something, I come here.")
("Previously, I come here.")

or in the second and third orders:
mi [cu] klama ti pu [ku]
mi klama ti pu
("I come here before something.")
("I come here, before.")
("I come here, previously.")

mi pu ku [cu] klama ti
mi pu ku klama ti
("I, before something, come here.")
("I, previously, come here.")

Note the change in what is elidable, especially in the first form.
Without the "ku", the "pu" would be a tag on sumti "mi", giving:

pu mi [cu] klama ti
pu mi klama ti
("Before me, someone unspecified comes here.")

which is quite different from the desired statement.  Note also, that
this plausible ellipsis can be expressed by translating it as an
adverb rather than as a prepositional phrase.  Making this change, we
see that the first form is now the one that is most like English
phrasing instead of the second form, as was true for the earlier
examples.

The 'adverbial' elliptical interpretation for the three operators are:

ca	"At the same time, ..." or "Simultaneously, ..."
ba	"Afterwards, ..." or "Later, ..."
pu	"Previously, ..." or "Earlier, ..."

We will explore the plausible interpretation of the ellipsis in more
depth in the section below on 'story time'.  For now, if you envision
this sentence in a stream of sentences, the time is being expressed
relative to the time that was set in some previous sentence, probably
the last one.  That previous time must have been explicitly set by a
time modifier sumti of the form we've been discussing, or implicitly
set by a statement that has an obvious mutually known time reference
such as the explicit:

li vo [cu] tcika
Four is the time-of-day.


15.3
selbri Tenses
selbri temci valsi

We can carry the ellipsis one step further, believe it or not.  Using
only the third form, we make the simple transformation from an awkward
English form:

mi pu ku [cu] klama ti
mi pu ku klama ti
("I, before something, come here.")
("I, previously, come here.")

to the semantically identical:

mi [cu] pu klama ti
mi pu klama ti
("I before-come here.")
("I did-come here.")
("I came here.")

We have eliminated the "ku", and the time-tagged modifier sumti has
become a time-tagged selbri, effectively identical to the English
simple past tense.  "ba" and "ca" similarly become identical to the
simple future tense and simple present tense.  The linguistic term for
the direct modification of the selbri with a tense is called
"inflection".

In spite of appearances, Lojban inflections are significantly different from English.  Every Lojbanist 
who hears:

"mi pu klama ti"

 intuitively remembers the full logical structure implied:

"mi pu [some ellipsized event abstraction bridi] klama ti vau"

where "vau" indicates the rest of the sumti places.

THESE PLACES COULD VERY WELL INCLUDE OTHER MODIFIER sumti, POSSIBLY 
INCLUDING OTHER TIME-TAGGED MODIFIER sumti

There are an infinite number of time events that can be inserted into
the bridi to make the time as explicit as you desire:

mi [cu] klama ti pu le nixli ba le ninmu [ku] [vau]
mi klama ti pu le nixli ba le ninmu
"I come here before the girl (and) after the woman."


15.4
Space Location Tenses
stuzi temci valsi

Everything we have said about time location modifier sumti applies to
space location, including that final simplification.  Unlike time
locations, space locations need not be tied to events, though events
can serve as location references:

vi	"at the location of ..."
		vi lenu mi [cu] zutse ti [kei] [ku]
		vi lenu mi zutse ti
		"at the location of my sitting here"
		vi la djan.
		"at the location of John"

va	"near the location of ..."
		va lenu mi [cu] zutse ti [kei] [ku]
		va lenu mi zutse ti
		"near the location of my sitting here"
		va la djan.
		"near the location of John"

vu	"far from the location of ..."
		vu lenu mi [cu] zutse ti [kei] [ku]
		vu lenu mi zutse ti
		"far from the location of my sitting here"
		vu la djan.
		"far from the location of John"

When ellipsized, these become the adverbial forms:

vi ku		"There, ..."
va ku		"Nearby, ..."
vu ku		"Yonder, ..."	 or "In the distance, ..."

They may also be ellipsized into simple tenses, which the following
examples demonstrate:

mi [cu] vi pensi  		"I here-think about..."
do [cu] va pensi  		"You there-think about..."
ko'a [cu] vu pensi		"It yonder-thinks about..."

The ellipses in the case of space locations have two interpretations.
In a narrative, the locations are relative to some predefined or known
location, as described above for tense.  For spontaneous conversation,
there is another more plausible interpretation that takes precedence:

mi vi ti [cu] pensi  		"I at-here think about..."
do va ti [cu] pensi  		"You near-here think about..."
ko'a vu ti [cu] pensi		"It far-from-here thinks about..."

or the more demonstrative:

mi vi ti [cu] pensi  		"I at-here think about..."
do vi ta [cu] pensi  		"You at-there think about..."
ko'a vi tu [cu] pensi		"It at-yonder thinks about..."

The latter forms require more active 'pointing', but mean roughly the
same as the former ones.

(Note that you can use demonstrative pro-sumti with time-tagged
modifiers as well as with location tags: "ba ti" means "after this".

You can have both time- and space- tagged modifier sumti:

mi ba le nu (mi) sipna kei [ku] vi le jubme [ku] cu citka
mi ba le nu (mi) sipna kei vi le jubme cu citka
"I, after (my) sleeping and at the table, eat"

By changing the order so that the more complicated modifier sumti is
against the "cu" (or at the end of the sentence), you can make elision
easier:

mi vi le jubme [ku] ba le nu (mi) sipna [kei] cu citka
mi vi le jubme ba le nu (mi) sipna cu citka
"I, at the table and after (my) sleeping, eat."

mi [cu] citka vi le jubme [ku] ba le nu (mi) sipna [kei] [ku]
mi citka vi le jubme ba le nu (mi) sipna
"I eat at the table after (my) sleeping."

You can also use a simple time-space tense to reference an elliptical
time and space:

mi [cu] cavi citka
mi cavi citka
"I then-and-there ate."

This is comparable to an acceptable English construction.  But you can
do more than this with Lojban elliptical simple tenses:

mi [cu] bavu citka
mi bavu citka
"I later-and-yonder (will) eat."

This, while of the same form, is not standard English, probably
because it is too uncommon.  Lojban, with no idiom, allows the
uncommon as readily as the common.

You can also work backwards from these time-space simple tenses to
attach both time and location to an event:

mi cavi la djan. [cu] citka
mi cavi la djan. cu citka
"I, at-the-same-time-and-place-where-John-does, eat."
"I, when-and-where-John-does, eat."

As with time modifiers, we can have an indefinite number of location
modifiers attached to a bridi, or we can have both time and space
modifiers attached to our heart's content.


15.5
Tenseless bridi - The Ultimate Ellipsis
temci claxu bridi

You are now hopefully better able to understand the ultimate ellipsis
that is implied when we omit tense.  It isn't that there is no time or
space reference; we have simply ellipsized to the fullest extent
possible.  The bridi is stated as true at some time, and at some
place, with both being elliptically omitted because they are
presumably obvious from the context.

Now you-there don't go yonder-sticking here-location-markers on every
there-noun or yonder-verb, do you?  For that matter, you don't stick
tenses on each of these either; it is presumed that unless explicitly
stated, all pieces of a sentence are at the same time and place, and
furthermore, that only the time of the verb needs to be mentioned.  In
Lojban, treat time and space both, as you do space location in
English; don't even bother putting it on the selbri unless it isn't
obvious.  If you don't need to specify time and space, stick with good
old "cu".


15.6
Determining The Elliptical Value
nu facki loi nalnunsku sumti

We need to pause here, and ensure that you are clear on how to
determine the elliptical value in a simple tense form of Lojban bridi.
There are conventions, some of which may be obvious; others are not
obvious, but are still the commonplace English ellipsis as well.

First, you can use tense to convey time relative to the present, or to
express the passage of time.  Context must be used to determine which
is intended.  Simple statements are generally expressed with reference
to the time the speaker is expressing the sentence:

mi [cu] pu se dicra	"I was interrupted."
mi [cu] ca kanro	"I am now/currently healthy."
mi [cu] ba vitke	"I will visit/I will be a visitor."

Thus far, everything appears to be like English.  If you leave the
time tense out, you must infer the time from the context.  It is
usually, but NOT NECESSARILY present tense.  It is perfectly legal to
say:

mi [cu] jbena
"I am-born to ..."

in the present, even though the event of your birth was in the past.
This can be seen by remembering the essential unity between nouns,
verbs, and adjectives in Lojban, and observing that this sentence can
also be translated:

"I am a born (to...) thing."

With this translation, it can be seen that it is true even with the
event having been in the past.

While it is not as easy for an English-speaker to see, the same holds
for future tense.

mi [cu] klama
"I go."

is one example that has a useful English counterpart.  We often say in
English, before leaving, "I'm going."  The untensed Lojban sentence
can similarly be taken such a statement of intent, potential, or
prediction.

When you insert a simple tense, for now you can assume that these
qualifications do not hold.  You are making an assertion of truth that
is time dependent.  Saying:

mi [cu] ca klama
"I am-now going ..."

you are asserting that you are moving towards your destination as you
speak.


15.7
Story Time
lisri temci

In narratives, things get more complicated.  The time at which that
the narrative is told is usually unimportant to the story.  The
contextual time-in-the-story is the critical reference.  In English
fairy tales, this is set by the opening line "Once upon a time".  In
other narratives, statements are used to initially set the time: "It
was a dark and stormy night."  The same techniques will work for
Lojban, though we will have to save "once upon a time" for a later
lesson.

The conventions we will present may seem abstract and complicated,
especially at first.  You need a significantly sized example, such as
the narrative at the end of this lesson.  An explanation of the
corresponding English conventions would be much more complicated.  The
complexity of English tenses is why non-fluent English speakers often
have misused and confusing time-tense in their sentence expressions.

For now, set narrative tenses at the beginning using simple tensed
modifier sumti like:

ca li vo
"At four (o-clock), ..."

ca le vlile tcima ke manku nicte
"On a violent-weathered type-of dark night"
"On a dark and stormy night"

In narratives, 'story-time' moves along as the story progresses.  It
is presumed that the event described by each sentence takes place some
time more or less after the previous one.  This is true, at least, if
the sentence is without explicit tense.  (It is possible, when using
only "cu" for total ellipsis of tense, to be referring to a past or
simultaneous event - we are talking about the normal 'flow' of a
story, though.)

'Story-time' proceeds as a flow whenever you do not specify a tense.
Specifying a tense may, or may not, advance the story-time, and it is
preferable to assume that it does not.  (There are a variety of ways
to explicitly change the 'story-time' that we will cover in later
lessons; we will learn one of the weaker methods here.

If you use a time-tense cmavo after the 'story-time' has been
established, then the tense should be treated as an offset from that
story time.  Specifically, it is best to presume it an offset from the
'story-time' at the end of the last sentence.  Thus, when you use the
tense cmavo "pu" or the adverbial modifier "puku", you are referring
to an event/time previous to the current 'story-time'.  If you use
"ca" or "caku", you are referring to a time/event simultaneous with
the 'story-time', which probably is unchanged from the previous
sentence.  If you use "ba" or "baku", you are referring to some time
after the current 'story-time'.

In general, such a tense-inflected or adverbial sentence in a
narrative does not 'reset' the 'story time', nor does an explicit
modifier sumti; the offset from story-time lasts just for the one
sentence.  The following sentence, if untensed, occurs a little while
after the last untensed sentence.  If tensed, the sentence is an
offset from the last offset time.  Meanwhile, story-time just flows
along at a regular or irregular rate from sentence to sentence.  The
amount that time advances is ambiguous unless we explicitly add a
modifier.

The only way you can effectively specify the jump in story-time is to
give an untensed sentence (so there is no offset involved) which has a
specific event built into it that can be the basis for calibrating the
new story-time.

We will learn in later lessons how to change the 'story time' even
more freely; an ability which is needed for flashbacks and look-aheads
that are common in narratives, as well as for expressing relative
times.

The following is a short but complex example of the various techniques
of manipulating story-time, showing the resulting time flow:

ca li vo [cu] slabu fasnu .i mi [cu] ba klama le zarci [ku] .i li xa
[cu] tcika le cnino fasnu [ku] .i mi [cu] ba klama le zarci [ku] .i pu
li bi [cu] lerci fasnu .i mi [cu] ba klama le zarci [ku]

Translating, we have:

"At 4 (initial story-time) old-event (observative).  I
will-later-(after the last sentence time)-go-to the
market. (Story-time passes between sentences.)  6 is the
(new-story-time) time-of-day of the new- event.  I
later-(without-resetting the last sentence time)-go-to the market.
Before 8, (not resetting story-time), late-event (observative).  I
after-(the last sentence time, but possibly before going to the
market, which is still the basis for story-time)-went-to the market."


15.8
Elliptical Location Tenses
nalnunsku stuzi temci valsi

In simple statements, location tenses are totally straight-forward.
The omitted tense says nothing about the location, though they might
be a slight inference that the event is occurring at the location of
the speaker.  There are few clear-cut conventions for location as a
tense, at least to the English speaker, since we don't use location
tenses in grammatical speech.  When you explicitly label a bridi with
a simple location inflection, you are then definitely relating the
location to the speaker's location.

In narrative, you can initially set the 'story place' with a
location-modifier sumti.  This is done in Star Wars, for example, with
"... in a galaxy far, far away ...".  (If you don't specify it,
presumably it doesn't matter, just as with time.  This is usually
true, for example, in stories which are jokes.)  After such an initial
setting, all events take place relative to the story reference unless
it is changed.  Unlike time, which naturally flows in a story,
location tends to be constant.  You reset story- location reference by
specifically stating a location-oriented (locative) bridi without a
location modifier or inflection.  As an example of this, after the
sentence "mi klama ti ta", the story- location moves from "ti" to "ta"
as an inherent part of the semantics of the bridi.

Once you have a 'story reference', using a location modifier or
inflection to describe an event or relationship bridi defines the
location of the bridi relative to the 'story reference'.  If the bridi
has no explicit location tense, the location is either presumed
unchanged from the previous sentence, or it may specify a new location
by the locative nature of the bridi.

Two features have not been shown in the examples we've presented.

In a sentence with either a time or location (or both) tense
inflection before the selbri, "cu" is never required.  It needn't even
be considered an elided marker.  This doesn't mean that you can't use
it.  In fact, it is often desirable to use "cu" even when it is
elidable after a complex sumti, or after a series of sumti expressed
before the selbri.  This makes it easier to pick out that selbri in
speech.  The tense labels work equally well, but since they are 'all
over the alphabet', you may wish to explicitly include "cu" in order
to be clearly understood.  This is especially important in 'noisy
environments', or possibly when the tense is a complex one.

If a narrative includes conversation that is supposed to be 'real',
then time and space references must be interpreted as if you were
there listening to the speaker in the story.  This can lead to a
fairly mind-boggling set of transformations if you try to analyze what
you are doing, but we manage quite fine in English.  Moreover, in some
narratives such as the stories told in 'The Arabian Nights', you have
narrative stories within narrative stories, sometimes nested several
levels deep.  English doesn't handle this well at all.

But for now, stick to simple tenses.