Intelligence: Intel is quite similar to what is currently known as
IQ, but it also includes mnemanic ability, reasoning,
and learning ability outside those measured by the written word.
Intelligence dictates the number of languages in which the character is
able to converse.* Moreover, intelligence is the forte of magic-users, for
they must be perspicacious in order to correctly understand magic and
memorize spells. Therefore, intelligence is the major characteristic of
magic-users, and those with intelligence of 16 or more gain a bonus of
10% of earned experience. Spells above 4th level cannot be learned by
magic-users with minimal intelligence, and intelligence similarly dictates
how many spells may be known and what level spells may be known, for
only the highest intelligence is able to comprehend the mighty magics
contained in 9th level spells. The tables below allow ready assimilation of
the effects of intelligence on all characters - and with regard to magicusers
in particular.

*Non-human characters typically are able to speak more languages than
are human characters, but intelligence likewise affects the upper limit of
their abilities as well, and there are racial limitations. (See CHARACTER RACES.)

Ability Score - General Information Possible Number of 
Additional Languages
(Months to learn)
Illusion/Phantasm Immunity* Wisdom Range 
for Monsters
0 Non-intelligent or not ratable - 0 - <>
1 Animal intelligence - 0 - <>
2 Semi-intelligent - 0 - <>
3 ^ - 0 - <>
4 ^ Min. INT for a half-elf character 0 - <>
5 Low intelligence Here or lower the character can only be a fighter 0 - 2-8
6 ^ Min.  INT for a halfling character 0 - ^
7 ^ Min.  INT for a gnome character 0 - ^
8 Average (human) intelligence Min.  INT for an elf character 1 (12 months) <+1y> - 3-12
9 ^ Min.  INT for a paladin or M-U character 1 (12 months) <+1y> - ^
10 ^ Min.  INT for use of 5th level magic spells 2 (12 months) <+2y> - ^
11 Very intelligent Min.  INT for an assassin character 2 (12 months) <+2y> - 4-16
12 ^ Min.  INT for use of 6th level magic spells 3 (12 months) <+3y> - ^
13 Highly intelligent Min.  INT for a ranger character 3 (11 months) <+2y9m> - 4-16
14 ^ Min.  INT for use of 7th level magic spells 4 (10 months) <+3y4m> - ^
15 Exceptionally intelligent Min.  INT for an illusionist character 4 (9 months) <+3y> - 8-18 (2d6 + 6)
16 ^ Min.  INT for use of 8th level magic spells 5 (8 months) <+3y4m> - ^
17 Genius Max. INT for a half-orc character 6 (7 months) <+3y6m> - 8-18 (2d6 + 6)
18 ^ Min.  INT for use of 9th level magic spells 7 (6 months) <+3y6m> cantrips ^
19 Supra-genius - 7 (5 months) <+2y11m> 1st 8-20 (4d4 + 4)
20 Supra-genius - 7 (4 months) 2nd ^
21+ Godlike intelligence - 7 (3 months) 3rd 9-24 (3d6 + 6)
22 ^ - 7 (2 months) 4th ^
23 ^ - 7 (1 month) 5th ^
24 ^ - 7 (Instantaneous) <?> 6th ^
25 ^ - 7 7th ^

* Spell immunities to illusion/phantasm spells.

Ability Score Chance to Know Each Listed Spell Minimum Number of Spells/Level Maximum Number of Spells/Level
9 35% 4 6
10-12 45% 5 7
13-14 55% 6 9
15-16 65% 7 11
17 75% 8 14
18 85% 9 18
19 95% 11 All
20 96% 12 ^
21 97% 13 ^
22 98% 14 ^
23 99% 15 ^
24 100% 16 ^
25 100% 17 ^

SA: All of the info on Intelligence Table II applies to rangers as well.

Notes Regarding Intelligence Table II:

Each and every magic-user character must employ the Table in order to
determine which and how many of each group of spells (by level) he or
she can learn. At first, only the 1st level group of spells are checked.
Successive level groups are checked only when the character reaches a
level at which the appropriate group of spells is usable by him or her.

Chance to Know Each Listed Spell pertains to the %percentage%
chance the character has by reason of his or her intelligence to learn any given spell
in the level group.
The character may select spells desired in any order he or she wishes.
Each spell may be checked only once.
Percentile dice are rolled, and if the number generated is equal to or less than the percentage chance shown, then the character can learn and thus know that spell
(it may be in his or her spell books - explained hereafter).
    Example: A character with an INT of 12 desires to know a charm person spell
    that he finds in a book or scroll, percentile dice are rolled, but the number
    generated is 52, so that spell is not understood and can not be used by the
    character (see, however, the paragraph below regarding the minimum
    number of spells knowable).

<make a note about reversed spells here>

Minimum Number of Spells/Level states the fewest number of spells by
level group a magic-user can learn. If one complete check through the
entire group fails to generate the minimum number applicable according
to intelligence score, the character may selectively go back through the
group, checking each spell not able to be learned once again. This process
continues until the minimum number requirement has been fulfilled. This
means, then, that certain spells, when located, can be learned - while
certain other spells can never be learned and the dice rolls indicate which
ones are in each category. Example: The magic-user mentioned above
who was unable to learn a charm person spell also fails to meet the
minimum number of spells he or she can learn. The character then begins
again on the list of 1st level spells, opts to see if this time charm person is
able to be learned, rolls 04, and has acquired the ability to learn the spell.
If and when the character locates such a spell, he or she will be capable of
learning it.

Maximum Number of Spells/Level: is the obverse of the minimum number
which can be known. According to the characterís intelligence, this
maximum number which the magic-user can possibly know (have in his or
her spell books) varies from 6 to an unlimited number. As soon as this
maximum is reached, the character may not check any further in the level

Change in Intelligence: If intelligence goes down or up for any reason,
and such change is relatively permanent, the magic-user must check again
as explained above far known spells by level group.

Acquisition of Heretofore Unknown Spells: Although the magic-user must
immediately cease checking to determine if spells are known after the first
complete check of each spell in the level group, or immediately thereafter
during successive checks when the minimum number of spells which can
be known is reached, it is possible to acquire knowledge of additional
spells previously unknown as long as this does not violate the maximum
number of spells which can be known. New spells can be gained from
captured or otherwise acquired spell books or from scrolls of magic spells.
In the latter event the scroll is destroyed in learning and knowing the new
spell or spells. (This subject is detailed more fully in the section explaining
magic-users as characters.)

Question: Please clear up an apparent rules contradic-
tion in the AD&D PH. On page 10 it gives a list
of how many spells a Magic-User can know, based on intel-
ligence and the chance for knowing them. But on page 26 it
states that the Magic-User can only cast a certain number of
spells, according to the level of the spell and the level of the
spell caster. Must the DM decide which table to use, or

Answer: The table on page 10 shows how many spells the caster
may know due to intelligence, not how many he/she can cast. These
spells are the ones which are written in the spell-casterís spell books.
The table on page 26 indicates what levels of spells and how many
from each level may be memorized at one time (from the spell
books) for casting at a later time. As the Magic-User increases in
levels, so does his/her ability to learn and memorize more spells. The
tables are designed to be used together, not separately.

Illusion/Phantasm Immunity (Immunities to Illusion/Phantasm Spells):
Beings of very high intelligence will not be fooled by illusion/phantasm
spells; they will note some inconsistency or inexactness which will prevent
their belief in the illusion. A being with a 19 intelligence will never believe
a 1st level illusion/phantasm spell, even if cast by a high-level spell-caster,
and will thus avoid all effects.
All effects noted are cumulative (e.g. a 20 intelligence gives immunity to first
and second level illusions).

Q: Exactly which spells from which
classes are first-level illusions?
A: Illusion/phantasm spells from the illusionist
?s first-level spell list are first-level
illusions, even when several classes can
cast them. Phantasmal force, for example,
is a first-level illusion/phantasm, even
though it is a third-level spell for magicusers.

Originally Posted by SuStel
Hey there, Gary!

There's always been some debate as to whether newly-created AD&D magic-users check the entire 1st level spell list for spells known immediately upon character creation, or if they only check spells as they come across them. I therefore have two questions:

1. How do you do it in your games (if at all)?

2. Which way did you have in mind when you wrote the book?

A spell can be known only when the character is able to use spells.
Thus the check is done when the new PC is seeking to fill his 1st level spell book.
As new levels are gained, and with that added spells, the player again checks for the PC.

We allowed the player to decide on which spell was to be known, then dicing to see if it was.
When all slots were filled, the process ended until a new level was gained.