Chapter 14: If Wishes Were Horses: The Lojban Connective System

12. Logical connection within tanru

As noted at the beginning of c14-§9, there is no logical connective in Lojban that joins selbri and nothing but selbri. However, it is possible to have logical connectives within a selbri, forming a kind of tanru that involves a logical connection. Consider the simple tanru “blanu zdani”, blue house. Now anything that is a blue ball, in the most ordinary understanding of the phrase at least, is both blue and a ball. And indeed, instead of “blanu bolci”, Lojbanists can say “blanu je bolci”, using a jek connective within the tanru. (We saw jeks used in c14-§11 also, but there they were always prefixed by “pe'e”; in this section they are used alone.) Here is a pair of examples:

✥12.1    ti blanu zdani
This is-a-blue type-of house.

✥12.2 ti blanu je zdani
This is-blue and a-house.

But of course ✥12.1 and ✥12.2 are not necessarily equivalent in meaning! It is the most elementary point about Lojban tanru that ✥12.1 might just as well mean

✥12.3    This is a house for blue inhabitants.

and ✥12.2 certainly is not equivalent in meaning to ✥12.3.

A full explanation of logical connection within tanru belongs rather to a discussion of selbri structure than to logical connectives in general. Why? Because although ✥12.2 happens to mean the same as

✥12.4    ti blanu gi'e zdani

and therefore as

✥12.5    ti blanu .ije ti zdani

the rule of expansion into separate bridi simply does not always work for tanru connection. Supposing Alice to be a person who lives in blue houses, then

✥12.6    la .alis. cu blanu je zdani prenu
Alice is-a (blue and house) type-of-person.

would be true, because tanru grouping with a jek has higher precedence than unmarked tanru grouping, but:

✥12.7    la .alis. cu blanu prenu
    .ije la .alis. cu zdani prenu
Alice is-a blue person,
    and Alice is-a house person.

is probably false, because the blueness is associated with the house, not with Alice, even leaving aside the question of what it means to say “Alice is a blue person”. (Perhaps she belongs to the Blue team, or is wearing blue clothes.) The semantic ambiguity of tanru make such logical manipulations impossible.

It suffices to note here, then, a few purely grammatical points about tanru logical connection. “bo” may be appended to jeks as to eks, with the same rules:

✥12.8    la teris. cu ricfu je nakni jabo fetsi
Terry is rich and (male or female).

The components of tanru may be grouped with “ke” both before and after a logical connective:

✥12.9    la .teris. cu [ke] ricfu ja pindi [ke'e]
    je ke nakni ja fetsi [ke'e]
Terry is (rich or poor)
    and (male or female).

where the first “ke … ke'e” pair may be omitted altogether by the rule of left-grouping, but is optionally permitted (as in bridi connection). In any case, both instances of “ke'e” may be elided.

The syntax of jeks is:

[na] [se] JA [nai]
parallel to eks and giheks.

Forethought tanru connection does not use geks, but uses guheks instead. Guheks have exactly the same form as geks:

[se] GUhA [nai]
Using guheks in tanru connection (rather than geks) resolves what would otherwise be an unacceptable ambiguity between bridi-tail and tanru connection:

✥12.10  la .alis. gu'e ricfu gi fetsi
Alice is both rich and female.

Note that giks are used with guheks in exactly the same way they are used with geks. Like jeks, guheks bind more closely than unmarked tanru grouping does:

✥12.11  la .alis. gu'e blanu gi zdani prenu
Alice is-a-(both blue and a-house) type-of-person.

is the forethought version of ✥12.6.

A word of caution about the use of logically connected tanru within descriptions. English-based intuition can lead the speaker astray. In correctly reducing

✥12.12  mi viska pa nanmu .ije mi viska pa ninmu
I see a man, and I see a woman.

to

✥12.13  mi viska pa nanmu .e pa ninmu
I see a man and a woman.

there is a great temptation to reduce further to:

✥12.14  mi viska pa nanmu je ninmu
I see a man and woman.

But ✥12.14 means that you see one thing which is both a man and a woman simultaneously! A “nanmu je ninmu” is a manwoman, a presumably non-existent creature who is both a “nanmu” and a “ninmu”.