
<PAGE>
 
                                                                       Exhibit 5
                                                          
                                                          
 ASHLAND INC, . P.O. BOX 381 . ASHLAND, KENTUCKY 41114 . PHONE (606) 329-3333
  
   THOMAS L. FEAZELL
   Senior Vice President,
   General Counsel and Secretary            March 20, 1998
   (606) 329-3403
   (606) 329-3559 (FAX)
  
   Ashland Inc.
   1000 Ashland Drive
   Russell, Kentucky 41169
   
   Dear Sirs:
   
           As Senior Vice President, General Counsel and Secretary of Ashland
   Inc. ("Ashland"), I have examined and am familiar with the Second Restated
   Articles of Incorporation and Bylaws of Ashland, both as amended. I am also
   familiar with the corporate proceedings taken by the Board of Directors of
   Ashland on January 28, 1998 to authorize the filing with the Securities and
   Exchange Commission of a Form S-4 Registration Statement covering
   $150,000,000 principal amount of Debt Securities (the "Debt Securities") of
   Ashland to be issued under an Indenture dated as of August 15, l989, as
   amended and restated as of August 15, 1990 (the "Indenture"), entered into by
   Ashland and Citibank, N.A. I have also examined originals or copies
   certified or otherwise identified to my satisfaction of such corporate
   records and other documents as I have deemed necessary or appropriate for
   purposes of this opinion.
      
        Based on the foregoing, I am of the opinion that:
        
           1. Ashland is a duly incorporated and validly existing corporation
   under the laws of the Commonwealth of Kentucky.
   
           2. The execution and delivery of the Indenture has been validly
   authorized; the Indenture has been duly executed and delivered by Ashland,
   constitutes a legal, valid and binding agreement of Ashland enforceable
   against Ashland in accordance with its terms (subject, as to enforcement of
   remedies, to applicable bankruptcy, reorganization, insolvency, moratorium or
   other laws affecting creditors' rights generally from time to time in effect
   and to the availability of equitable remedies); and the Debt Securities when
   duly executed and authenticated on behalf of Ashland and issued and sold in
   accordance with such corporate proceedings and the Indenture, will be validly
   authorized and issued and will constitute valid and binding obligations of
   Ashland enforceable against Ashland in accordance with their terms (subject
   as aforesaid) and will be entitled to the benefits of the Indenture.
   
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   Ashland Inc.
   March 20, 1998
   Page 2
    

            I know that I am referred to under the heading "Legal Matters" in
   the Registration Statement on Form S-4 and related Prospectus of Ashland with
   respect to the Debt Securities, filed with the Securities and Exchange
   Commission, and consent thereto and to the filing of this opinion as an
   Exhibit to such Registration Statement.
                                                 
                                    Very truly yours,
                                    
                                    /s/ Thomas L. Feazell 

                                    Thomas L. Feazell 
                                    
