<PAGE>
 
                                                                    EXHIBIT 8(d)


                     SKADDEN, ARPS, SLATE, MEAGHER & FLOM
                               919 THIRD AVENUE
                           NEW YORK, NEW YORK 10022
                                (212) 735-3000




                                              January 30, 1996



Independent Insurance Group, Inc.
One Independent Drive
Jacksonville, Florida 32276

Ladies and Gentlemen:

     We have been acting as counsel to Independent Insurance Group, Inc. (the
"Company") in connection with the transactions contemplated by the Agreement and
Plan of Merger, dated as of October 19, 1995 and as amended as of January 25,
1996, by and among the Company, American General Corporation, and AGC Life
Insurance Company, a wholly-owned subsidiary of American General Corporation
(the "Merger Agreement"). The delivery of an opinion at the Effective Time, in
substantially the form hereof, is a condition to the obligations of the Company
to consummate the Merger pursuant to Section 8.2(b) of the Merger Agreement. All
capitalized terms used herein, unless otherwise specified, shall have the
meanings ascribed to them in the Merger Agreement.

     In rendering our opinion, we have examined and relied upon the accuracy and
completeness of the facts, information, covenants, statements and
representations contained in originals or copies, certified or otherwise
identified to our satisfaction, of the Merger Agreement, representations
referred to in Section 7.9 of the Merger Agreement and such other documents as
we have deemed necessary or appropriate as a basis for the opinion set forth
below as well as other statements, representations and assumptions.  Our opinion
is expressly conditioned on, among other things, the accuracy as of the date
hereof, and the continuing accuracy of all of such facts, information,
covenants, statements and representations up to and including the Effective
Time.
<PAGE>
 
Independent Insurance Group, Inc
January 30, 1996
Page 2



     In our examination, we have assumed the genuineness of all signatures, the
legal capacity of natural persons, the authenticity of all documents submitted
to us as originals, the conformity to original documents of all documents
submitted to us as certified or photostatic copies and the authenticity of the
originals of such documents. We have also assumed that the contemplated
transactions will be consummated at the Effective Time in accordance with the
terms of the Merger Agreement. In addition, our opinion is expressly conditioned
on, among other things, the assumptions that at or prior to the Effective Time,
we will be provided with officers' certificates executed by executives of the
Company, American General Corporation, and AGC Life Insurance Company, in form
and substance satisfactory to us and on which we may rely, as to certain facts
relating to, and knowledge and intentions of, the Company, American General
Corporation, and AGC Life Insurance Company, and certain facts relating to the
Merger.

     In rendering our opinion, we have considered the applicable provisions of
the Internal Revenue Code of 1986, as amended (the "Code"), Treasury regulations
promulgated thereunder, pertinent judicial authorities, interpretive rulings of
the Internal Revenue Service and such other authorities as we have considered
relevant. It should be noted that statutes, regulations, judicial decisions and
administrative interpretations are subject to change at any time and, in some
circumstances, with retroactive effect. A material change in the authorities or
the facts, information, covenants, statements, representations or assumptions
upon which our opinion is based could affect our conclusions.

     Based solely upon the foregoing, we are of the opinion that, under current
law:

     The Merger would qualify as a reorganization pursuant to Section 368(a) of
     the Code, and that the Company, American General Corporation, and AGC Life
     Insurance Company would each be a party to that reorganization within the
     meaning of Section 368(b) of the Code.

Except as set forth above, we express no opinion to any party as to any
consequences of the Merger or any transactions related thereto. This opinion is
for your benefit and is not to be used, circulated, quoted or otherwise referred
to for any purpose, excluding the Proxy Statement-Prospectus which will be
included in

<PAGE>
 
Independent Insurance Group, Inc
January 30, 1996
Page 3


the Registration Statement on Form S-4 (the "Registration Statement") filed with
the Securities and Exchange Commission (the "Commission") under the Securities
Act of 1933, as amended (the "Securities Act").

     In accordance with the requirements of Item 601(b)(23) of Regulation S-K
under the Securities Act, we hereby consent to the filing of this opinion as an
Exhibit to the Registration Statement. In giving this consent, we do not admit
that we come within the category of persons whose consent is required under
Section 7 of the Securities Act or the rules and regulations of the Commission
thereunder.

 
                                        Very truly yours,


                                        /s/ SKADDEN, ARPS, SLATE,
                                            MEAGHER & FLOM

                                        SKADDEN, ARPS, SLATE, MEAGHER & FLOM