While that has been true for human history to date, it isn't any more. Any laptop with a couple of terabytes can carry an effective picture/video dictionary, and a few Moores from now a hologram dictionary. And this isn't simply a quibble without consequences; I've just given a conference presentation in which I argued that in the case of Persistent Vegetative State, where the nature of the condition is debated and the diagnostic criteria variable, an ostensive definition made up of a number of video clips would be more satisfactory than the current definition based only in (weasel) words.
Swift's philosophers, who floated
"...a Scheme for entirely abolishing all Words whatsoever; and this was urged as a great Advantage in Point of Health as well as Brevity. For it is plain, that every Word we speak is in some Degree a Diminution of our Lungs by Corrosion, and consequently contributes to the shortning of our Lives. An Expedient was therefore offered, that since Words are only Names for Things, it would be more convenient for all Men to carry about them, such Things as were necessary to express the particular Business they are to discourse on. And this Invention would certainly have taken Place, to the great Ease as well as Health of the Subject, if the Women in conjunction with the Vulgar and Illiterate had not threatned to raise a Rebellion, unless they might be allowed the Liberty to speak with their Tongues, after the manner of their Ancestors; such constant irreconcilable Enemies to Science are the common People. However, many of the most Learned and Wise adhere to the New Scheme of expressing themselves by Things, which hath only this Inconvenience attending it, that if a Man's Business be very great, and of various kinds, he must be obliged in Proportion to carry a greater bundle of Things upon his Back, unless he can afford one or two strong Servants to attend him. I have often beheld two of those Sages almost sinking under the Weight of their Packs, like Pedlars among us; who, when they met in the Streets, would lay down their Loads, open their Sacks, and hold Conversation for an Hour together; then put up their Implements, help each other to resume their Burthens, and take their Leave.
But for short Conversations a Man may carry Implements in his Pockets and under his Arms, enough to supply him, and in his House he cannot be at a loss: Therefore the Room where Company meet who practise this Art, is full of all Things ready at Hand, requisite to furnish Matter for this kind of artificial Converse.
Another great Advantage proposed by this Invention, was that it would serve as a Universal Language to be understood in all civilized Nations, whose Goods and Utensils are generally of the same kind, or nearly resembling, so that their Uses might easily be comprehended. And thus Embassadors would be qualified to treat with foreign Princes or Ministers of State to whose Tongues they were utter Strangers."
- would have loved it. More to Stewart and Cohen's point, treating "with foreign Princes or Ministers of State to whose Tongues they were utter Strangers" is a reasonable beginning to interalien communication problems.
When the point was made to Stewart & Cohen, they replied "An excellent point, well made. Many thanks for your interest. If we ever do a sequel or a new edition, we'll bear this in mind." -- which I suspect to be an automatic reply along the lines of "John Smith is out of the office", but I add it for the sake of completeness.